Circular No. 22/2009/TT-BTNMT on exploration, classification of reserves and resources of clay deposits

CIRCULAR

Provisions on exploration, classification of reserves and resources of clay deposits

_________________

MINISTER OF NATURAL RESOURCES AND ENVIRONMENT

Pursuant to Decree No. 25/2008/NĐ-CP dated March 4, 2008 of the Government stipulating the functions, tasks, powers, and organizational structure of the Ministry of Natural Resources and Environment;

Pursuant to Decree No. 160/2005/NĐ-CP dated December 27, 2005 of the Government detailing and guiding the implementation of the Minerals Law and the Law Amending and Supplementing Certain Articles of the Minerals Law;

Considering the proposal of the Director of the Office of the Mineral Reserves Evaluation Council and the Director of the Legal Department,

c) Enterprises may be granted permission for no more than one block out of the total three dual-frequency blocks (FDD) B

Chapter 1.

GENERAL PROVISIONS

Article 1. Scope of Regulation

This Circular stipulates requirements for the work of exploration, classification of reserves and resources of clay deposits.

Article 2. Applicability

This Circular applies to state management agencies for minerals; organizations conducting basic geological surveys on mineral resources; organizations and individuals surveying, exploring, and mining minerals; and other related organizations and individuals.

Article 3. Explanation of Terms

In this Circular, the following terms shall be understood as follows:

1. Clay is a group of rocks primarily composed of clay minerals (hydromica, kaolinite, montmorillonite, illite...), with particle sizes not exceeding 0.01 mm.

Depending on the degree of cohesion and compaction, clay is classified into clay, claystone, and shale.

2. Clay is a weakly consolidated sedimentary product that forms a pliable mass when mixed with water, easily molded into shapes which can be preserved, retains its shape when dried or baked, and becomes hard and durable upon firing at appropriate temperatures.

3. Claystone is a compact rock that does not disintegrate in water, formed through compaction and diagenesis processes from clay. Claystone has a mineral composition similar to that of clay.

4. Shale is a metamorphic rock consisting of tight slate-like layers made up of hydromica, chlorite, sometimes kaolinite, other clay minerals, quartz, feldspar, and non-clay minerals.

Chapter 2.

CLASSIFICATION OF RESERVES AND RESOURCES OF CLAY DEPOSITS

Article 4. Classification of reserves and resources of clay deposits

1. Resources of clay deposits are divided into two groups:

a) Determined resource group;

b) Predicted resource group.

2. The determined resource group is further divided into two types: reserves and resources.

Article 5. Classification of reserves and resources of clay deposits

1. Basis for classifying reserves and resources of clay deposits

a) Geological study level, including: certain, reliable, estimated, and predicted;

b) Level of investment project feasibility studies for mine construction projects, including: investment project feasibility studies for mine construction projects (feasibility studies), investment reports for mine construction projects (pre-feasibility studies), and general studies;

c) Economic efficiency level, including: economically viable, potential economic viability, and unclear economic viability.

2. Classification of reserves and resources of clay deposits

a) Reserves of clay deposits are classified into three levels: 111, 121, and 122;

b) Determined resources of clay deposits are classified into six levels: 211, 221, 222, 331, 332, and 333;

c) Predicted resources of clay deposits are classified into one level: 334.

3. Coding of reserve and resource levels of clay deposits

a) The first digit indicates the level of economic viability: number 1 - economically viable; number 2 - potential economic viability; number 3 - unclear economic viability;

b) The second digit indicates the level of investment project feasibility studies for mine construction: number 1 - feasibility studies for investment projects for mine construction; number 2 - pre-feasibility studies for investment projects for mine construction; number 3 - general studies;

c) The third digit indicates the level of reliability of geological studies: number 1 - certain; number 2 - reliable; number 3 - estimated; number 4 - predicted.

Article 6. Requirements for the level of research and delineation of reserve grade 111

1. Requirements for the level of geological research

a) Must accurately determine the morphology, size, position, folding, pattern of shape variation, and internal structure of the clay body, as well as the presence of major fractures;

b) Must accurately divide the clay body into groups and layers with distinct characteristics, clarifying the quantity, distribution area, and size of barren or non-compliant layers; the spatial location of each type of clay must be determined accurately.

c) The quality of the clay must be confirmed firmly and must meet the specified reserve calculation criteria for each block; the technological properties of the clay throughout the mine must be studied to the extent that the field of application of each type of clay can be determined. Test data on technological samples must meet the requirements for selecting processing technology procedures;

d) Hydrogeological conditions of the mine must be thoroughly researched to accurately calculate the amount of water flowing into the mining works; all technical mining conditions such as thickness, volume, and mechanical properties of the clay and overburden rock have been fully studied; dynamic geological phenomena have been clarified;

e) The reliability of the reserves must ensure a minimum of 80%.

2. Requirements for the delineation of reserve boundaries.

The boundary of grade 111 reserves is delineated within the range of exploration works cutting through the clay body, provided that the distance between the works ensures only one unique delineation plan for the ore body and intercalated rock layers, and has an appropriate density of works as stipulated in the annex attached to this Circular.

3. Requirements for the level of research on investment in construction of mine works

a) An investment project for constructing mine works has been established;

b) Suitable technical and processing technologies for clay raw materials have been selected;

c) The reserve area does not lie within prohibited or temporarily prohibited mineral activity zones; mining and processing activities within the reserve boundary do not affect the surrounding environment or, if they do, measures to mitigate their impact have been chosen to minimize the effects of mining and processing on the environment;

d) A reclamation or environmental restoration plan after mine closure has been selected.

4. Requirements for economic efficiency level

The results of the research on investment in construction of mine works have proven that the exploitation and processing of clay at the mine is economically viable at the time of establishing the investment project.

Article 7. Requirements for the level of research and delineation of reserve grade 121

1. Requirements for the level of geological research shall be carried out according to Clause 1 of Article 6 of this Circular.

2. Requirements for the delineation of reserve boundaries shall be carried out according to Clause 2 of Article 6 of this Circular.

3. Requirements for the level of research on investment in construction of mine works

a) An investment construction report for mine works has been prepared or temporary reserve calculation criteria recognized by the Mineral Reserve Evaluation Council have been established;

b) Preliminary selection of suitable technical and processing technologies for clay raw materials has been made;

c) The reserve area does not lie within prohibited or temporarily prohibited mineral activity zones; mining and processing activities within the reserve boundary do not affect the surrounding environment or, if they do, preliminary measures to mitigate their impact have been chosen;

d) A preliminary reclamation or environmental restoration plan after mine closure has been selected.

4. Requirements for economic efficiency level

The investment construction report for mine works has proven or, through comparison with operating mines with similar geological conditions, has shown that the exploitation and processing of clay at the mine is economically viable at the time of preparing the investment report.

Article 8. Requirements for the level of research and delineation of reserves at the 122 grade

1. Requirements for the level of geological research

a) The basic conditions of the clay bed's position and shape, as well as the presence of major faults must be determined;

b) The main lithological types of clay must be fully identified, but detailed spatial distribution of them does not need to be delineated;

c) The average thickness of the clay bed and the number of interbedded layers that do not meet the internal reserve calculation criteria must be determined, even if they cannot yet be accurately delineated in space;

d) The quality of the clay must be reliably confirmed and meet the reserve calculation criteria for each block; different types of clay must be classified, although their exact spatial distribution cannot be delineated; the technological properties of the clay must be studied to the extent necessary to determine the field of application for each type of clay; technical test data must provide the necessary information for selecting the processing technology;

đ) Hydrogeological, engineering geological characteristics, and mining technical conditions must be studied to the extent necessary to determine the number of water-bearing strata and their water richness, predict the amount of water likely to flow into the mining works, and determine the volume of overburden, even though their detailed spatial distribution cannot be determined;

e) The reliability of the reserves must ensure a minimum of 50%;

2. Requirements for reserve calculation boundary demarcation

The boundaries of the reserves must be delineated within the scope of drilling, exploration excavation works, and detailed sampling results from these works. For mines with uncomplicated geological structures where the thickness and quality are relatively stable, it is permissible to extrapolate based on geological and geophysical data from ore encounter wells or from higher-grade reserve boundaries. The extrapolation distance must not exceed half the distance between the exploration works already defined for this reserve grade;

3. Requirements for the level of research and construction investment for mine projects and requirements for economic efficiency are implemented according to the provisions of Clause 3 and Clause 4, Article 7 of this Circular;

Article 9. Requirements for the level of research and delineation of resources at grades 211, 221, and 331

1. Requirements for the level of geological research and delineation of resource boundaries

The requirements for the level of geological research and delineation of resource boundaries for grades 211, 221, and 331 are implemented according to the provisions of Clause 1 and Clause 2, Article 6 of this Circular;

2. Requirements for the level of research and construction investment for mine projects and economic efficiency:

a) Resource grade 211

An investment project for constructing mine works has been established, proving that under current technological, socio-economic, environmental, and other conditions at the time of project establishment, exploiting and processing clay from this resource is not economically viable. However, in the future, exploitation and processing may become economically viable due to scientific progress, changes in socio-economic, environmental, and legal conditions;

b) Resource grade 221

A preliminary report on investment for constructing mine works has been established, proving that under current technological, socio-economic, environmental, and other conditions at the time of report establishment, exploiting and processing clay from this resource is not economically viable. However, in the future, exploitation and processing may become economically viable due to scientific progress, changes in socio-economic, environmental, and legal conditions;

c) Resource grade 331

No study on investment for constructing mine works has been conducted, and it has not been determined whether exploiting and processing clay from this resource is economically viable or has potential economic viability, but geological research results have confirmed the certain existence of this resource.

Article 10. Requirements for the level of research and delineation of resource levels 222 and 332

1. Requirements for the level of geological research and delineation of resource boundaries

The requirements for the level of geological research and delineation of boundaries for resource levels 222 and 332 shall be carried out in accordance with the provisions of Clause 1 and Clause 2, Clause 2, Article 8 of this Circular.

2. Requirements for the level of investment construction project research and economic efficiency.

a) Resource level 222

The requirements for the level of investment construction project research and economic efficiency shall be carried out in accordance with the provisions of Point b, Clause 2, Article 9 of this Circular.

b) Resource level 332

Investment construction project research has not been conducted, and it has not yet been determined whether exploiting and processing clay from this resource source is economically viable or has potential economic viability, but the results of geological research have confirmed the reliability of this resource source.

Article 11. Requirements for the level of research and delineation of resource level 333

1. Requirements for the level of geological research and delineation of resource boundaries

a) Must determine the basic characteristics of the shape, position, and distribution of clay bodies;

b) Must preliminarily determine the thickness, structure, and stability of the clay body;

c) The quality of the clay must be preliminarily determined based on the results of sampling from natural exposures, cleared sites, trenches, wells, drilling, or extrapolating from adjacent areas with more detailed geological research;

d) Natural factors determining mining conditions do not necessarily require detailed research, mainly being initially understood and similar to nearby areas that have been more thoroughly researched.

2. Requirements for delineation of resource boundaries

The resource boundary 333 is delineated within the range of clay formations, according to exploration works meeting resource estimation criteria and permitted extrapolation based on structural boundaries and favorable rock systems for clay formation, combined with geophysical data and some drilling, excavation works, or from the boundaries of higher-level reserves and resources.

3. Requirements for the level of investment construction project research and economic efficiency

Investment construction project research has not been conducted, and it has not yet been determined whether exploiting and processing clay from this resource source is economically viable or has potential economic viability.

Article 12. Requirements for the level of research and delineation of resource level 334

Requirements for the level of geological research and delineation of resource level

a) Must establish signs of clay presence and favorable geological premises for clay formation;

b) The location, thickness, and quality of the clay must be determined based on sporadic sampling results at exposures, or inferred from mines or outcrops with similar geological conditions that have been more thoroughly researched.

2. Requirements for delineation of resource boundaries

Resource level 334 is primarily inferred based on regional basic geological investigation materials on mineral resources at a scale of 1:25,000 - 1:200,000, favorable geological premises and signs for clay formation, or inferred from mines that have been more thoroughly researched under similar geological conditions.

3. Requirements for the level of investment construction project research and economic efficiency

For this resource level, there is no requirement for data on investment construction project research and assessment of economic efficiency.

Chapter 3.

CLASSIFICATION OF PROSPECTING MINES

Article 13. Basis for Grouping Exploration Mines

1. Based on the shape, size of clay bed bodies, the complexity of geological structure of the mine, the stability in thickness, quality, and internal structure of the clay bed bodies.

2. Based on quantitative indicators to assess the degree of variation in conditions for grouping exploration mines.

3. Based on argumentation and specific evaluation of the main area of clay bed bodies, which accounts for not less than 70% of the mine's reserves.

Article 14. Grouping Exploration Mines

1. Simple Mine Group (I).

2. Relatively Complex Mine Group (II)

3. Complex Mine Group (III).

Article 15. Conditions for Grouping Exploration Mines

1. Simple Mine Group (I)

Includes mines or sections of mines in layer or lens form, large and medium sizes, lying horizontally or gently inclined with a simple geological structure, clay product storage coefficient greater than 0.8 and simple shape, perimeter variation coefficient (μ) less than 1.4; stable thickness, thickness variation coefficient (Vm) not exceeding 40%; even distribution of major beneficial and harmful components and variation coefficient (Vc) not exceeding 40% throughout the clay body.

2. Relatively Complex Mine Group (II)

Includes mines or sections of mines in layer or lens form, any size, simple geological structure, clay product storage coefficient ranging from 0.6 to 0.8 and complex shape, perimeter variation coefficient (μ) ranging from 1.4 to 1.8; unstable thickness, thickness variation coefficient (Vm) ranging from over 40% to 100%; uneven distribution of major beneficial and harmful components and variation coefficient (Vc) ranging from 40% to 100% throughout the clay body.

3. Complex Mine Group (III)

Includes mines or sections of mines in layer or lens form, any size, very complex geological structure, clay product storage coefficient below 0.6 and very complex shape, perimeter variation coefficient (μ) greater than 1.8; very unstable thickness, thickness variation coefficient (Vm) over 100%; highly uneven distribution of major beneficial and harmful components and variation coefficient (Vc) over 100% throughout the clay body.

Chapter 4.

REQUIREMENTS FOR CLAY MINE EXPLORATION WORK

Article 16. General Requirements for Clay Mine Exploration Work

1. Basic investigation, survey, and exploration of clay must follow the sequential principles of mineral geological investigation.

2. Must collect complete geological data and reliable exploitation conditions necessary for research and investment construction of mine projects; delineate areas and depths with the greatest potential for exploitation.

3. The task of clay mine exploration work is to detail the characteristics of the mine's geological structure; origin, distribution characteristics, shape, and position of the clay body; must evaluate reserves, resources, and quality and technological properties of the clay; detail geological hydrogeological and engineering geological conditions and mining conditions; determine clearly associated minerals and beneficial components within the clay body and overburden layers, their exploitable and recoverable capacity; evaluate the volume of overburden and factors affecting the ecological environment.

4. Must conduct exploration work for all clay mines across the entire area and depth where the clay body exists.

Article 17. Requirements for Topography and Geodetic Work

1. The topography of the mine must be surveyed in detail at a scale of 1 : 5 000 – 1 : 1 000 depending on its size, complexity of terrain, and intended use. Topographic maps must be established according to current regulations on geodetic work in mineral exploration.

2. All exploration works must determine coordinates and elevations and must relate to the National Coordinate Network in accordance with current geological geodetic regulations.

Article 18. Requirements for Exploration Techniques

1. Requirements for Geological Research Work

Clarify the characteristics of the geological structure of the mine, the origin of formation, degree of petrographic alteration, rock facies, shape, attitude conditions, fold structures, and the degree of structural destruction of the claystone body; it is necessary to establish a geological-petrographic map of the mine at a scale of 1: 5 000 - 1: 1 000 depending on the size and complexity of the geological conditions of the mine, along with appropriate cross-sections and stratigraphic columns; a regional geological map at a scale of 1: 25 000 – 1: 10 000 must also be prepared.

1. Requirements for Exploration Works

a) In exploring claystone mines, shallow drilling, deep drilling, inclined drilling, vertical drilling, trench lines, single trenches, pits, wells, and other surface clearance works may be used. The selected exploration works must be suitable for the attitude conditions, depth distribution, geological structure, morphology of the claystone body, and the thickness and characteristics of the overburden.

b) Trench lines and single trenches for surface research must be arranged perpendicular to the direction of the parent rock. The minimum width of the trench is 0.8 – 1.0 meters.

c) Drilling works for deep research must ensure that the core sampling ratio through the claystone layer is not less than 80%. If there are intercalated layers or lenses within the claystone layer with different components and quality, in addition to the general core sampling ratio for the entire claystone layer, separate core sampling ratios for each layer must be determined.

d) All exploration works must cut through the full thickness of the claystone body within the exploration boundary.

3. Requirements for Arrangement of Exploration Works

a) It is necessary to arrange exploration works and select exploration networks to ensure comprehensive research of the claystone body regarding its geological structural characteristics, morphology, dimensions, attitude conditions, stability in terms of thickness and quality of the claystone body.

b) The orientation density of exploration works for claystone mines shall be carried out in accordance with the provisions set forth in the Appendix attached to this Circular.

c) Requirements for Exploration Documentation

All exploration works, mining works, natural and artificial exposures at the mine must be described, mapped geologically, and original documentation must be promptly, fully, and accurately prepared in accordance with current regulations on preparing original documentation in mineral exploration and reflected on actual documentation maps.

Article 19. Requirements for Sample Collection and Processing

1. Requirements for Sample Collection Work

a) All exploration and mining works encountering claystone at the mine must be sampled for quality research. Sampling results must be included in the original documentation and must be checked against geological descriptions.

b) The method of sampling, cross-sectional area, and length of samples, quantity and distance between samples are determined based on the lithological types, morphology, internal structure, geological boundary characteristics, degree of variation of main components, and distribution of lithological types and claystones.

c) Samples must be taken layer by layer and separately for different lithological types of claystones and surrounding rocks. The length of the sample ranges from 1 meter to 2 meters, determined based on the thickness of the claystone body and the thickness of the non-compliant interbedded layers. When the product layer and claystone quality are uniform, the sample length increases up to 3 meters or 4 meters. For high-value claystones (refractory clay, bentonite...), the sample length is 0.5 meters, and when selective mining of specific claystone types is required, the sample length decreases to 0.3 meters to 0.4 meters. Separate samples must be taken for non-compliant layers or barren rock within the claystone body. If selective mining is not possible, these layers must be included in the sample composition.

d) In drill holes, samples must be continuously collected for all lithological types of claystones. Segments with different core sampling ratios must be sampled separately. Samples can be taken from the entire core or half-core, then processed and reduced to the required volume for research.

đ) In excavation works, samples are taken along grooves with a cross-section of 3 cm x 5 cm or 5 cm x 10 cm.

e) Test samples must be representative, containing chemical composition, mineralogical properties, physical and mechanical properties, particle size, hardness, and other properties consistent with the average composition of each type or style of claystone or the entire deposit. The quantity of test samples is agreed upon with the testing agency.

g) Large bulk samples are taken in quantities of 3 to 5 samples. Each large bulk sample must be accompanied by 4 to 5 small bulk samples and room humidity samples for checking and comparison. For brick and tile clay, the number of large bulk samples may be fewer or this type of sample may not be taken. The volume of large bulk samples depends on the structure of the claystone layer and usually varies from 1 to 3 meters.³.

2. Requirements for Sample Processing Work

The processing and reduction of samples for chemical component analysis are carried out according to a processing scheme established for each mine. The accuracy of the processing scheme and the reduction factor K must be verified using data from similar mines or mining documentation. The sample processing scheme is established according to the formula Q = Kd, where the factor K is 0.05 when the quality of the claystone is stable and 0.1 when the quality of the claystone is unstable or the harmful impurity content in the claystone approaches the allowable limit of the reserve calculation index. All samples for chemical component analysis must be processed to a particle size of 0.074 mm before analysis.²wherein: the coefficient K shall be taken as 0.05 when the quality of claystone is stable, and as 0.1 when the quality of claystone is unstable or the harmful impurity content in the claystone approaches the permissible limit of the storage capacity index. All samples for chemical component analysis must be processed to a particle size of 0.074mm.

Article 20. Requirements for analytical and sample testing work

1. Requirements for analytical work

a) The chemical composition of clay rock shall be determined by chemical analysis methods, spectroscopy, or other methods prescribed by competent authorities;

b) For clay used to produce cement, the basic sample must analyze SiO₂, Al₂O₃, Fe₂O₃, MKN components, and the group sample must analyze SiO₂, Al₂O₃, Fe₂O₃, FeO, CaO, MgO, MKN, SO₃kWp, kW₂O₅, K₂O, Na₂O, TiO₂, Cl^- components;

c) For clay used to produce refractory materials, porcelain, pottery, paper, rubber, and flavorings, the group sample must analyze SiO₂, Al₂O₃, Fe₂O₃, TiO₂, MKN components, and the group sample must analyze SiO₂, Al₂O₃, Fe₂O₃, FeO, CaO, MgO, MKN, SO₃, K₂O, Na₂O, TiO₂ components. If the clay contains gypsum, SO₃ component analysis must be conducted on the entire basic sample;

d) For bentonite, the basic sample must analyze SiO₂, Al₂O₃, Fe₂O₃, CaO, MgO, K₂O, Na₂O, binder coefficient, total cation exchange, and the group sample must analyze SiO₂, Al₂O₃, Fe₂O₃, FeO, CaO, MgO, MKN, SO₃, K₂O, Na₂O, TiO₂ components;

e) For clay used to produce refractory materials, building ceramics, porcelain, and keramzit, particle size distribution must be studied. The amount of fragmented material, size and composition of large inclusions, particle size fractions, and plasticity of the clay must be determined;

f) Technical ceramic characteristics must be studied for clay used to produce refractory materials, building ceramics, porcelain, and keramzit. Drying sensitivity, suitable firing temperature, dry tensile strength limit, temporary compressive and flexural strength after firing at appropriate temperatures, air shrinkage, firing shrinkage, water absorption after firing at appropriate temperatures, water permeability, and forming moisture content must be determined;

2. Requirements for sample testing work

a) The reliability of chemical analysis results must be evaluated through internal, external, and arbitration analyses;

b) Analytical testing work must be carried out regularly and systematically. Testing must be performed with different particle sizes and main chemical components if the storage index criteria are specified;

c) External analysis samples must be part of the internally analyzed samples. Both external and internal testing samples must represent all types of clay and levels of content for each basic analysis period;

d) When dividing content levels, attention must be paid to the content levels of the storage index criteria. The number of testing samples must be 5% of the total number of basic samples. In cases where the basic samples are few, the number of testing samples must not be less than 30 samples per content level or 100% of the basic samples must be tested;

e) In cases where external analysis detects systematic errors in basic analysis, arbitration analysis must be conducted in laboratories with higher analytical capabilities. Arbitration analysis samples are the retained samples from the basic analysis, except that the remaining portion of the basic analysis sample may be used. Arbitration analysis samples must have been externally analyzed. The number of arbitration analysis samples must be 30-40 samples per content level with systematic errors. If arbitration analysis detects systematic errors in basic analysis, the cause must be clarified and corrective measures taken, including re-analyzing the content level with systematic errors or allowing the use of adjustment factors. If the sample testing analysis process follows a different procedure, it must be accepted by the Mineral Reserves Evaluation Council;

f) The quality of particle size analysis of clay must be systematically checked by reanalyzing 5% to 10% of the samples immediately in the basic analysis room. The deviation between basic analysis and testing analysis must not exceed ± 1% weight;

g) The sampling inspection process, number of testing samples, analysis method, and handling of testing analysis data must comply with current regulations.

Article 21. Requirements for evaluating minerals and accompanying useful components

1. Samples must be taken and analyzed for mineralogical, chemical, physical-mechanical properties, and elements of overburden and interbedded rocks from the initial stages of exploration to detect and recover minerals and accompanying useful components during exploitation.

2. The evaluation of minerals and accompanying useful components shall be carried out in accordance with specific regulations issued by the Minister of Natural Resources and Environment.

Article 22. Requirements for studying clay rock quality

1. It is necessary to accurately determine the suitability for intended uses; assess the potential for use in other industrial sectors, especially those with high economic efficiency.

2. It is necessary to determine the usability of clay rock in industry based on its characteristics including chemical composition, particle size, mineralogical composition, fire resistance, water absorption, sintering ability, bonding capacity, dispersion, plasticity, mechanical strength after drying and firing, sensitivity, swelling, adhesion, and cation exchange capacity.

3. It is necessary to determine the technological properties of clay rock, select appropriate and efficient processing technology; assess the usability of overburden rock.

Article 23. Requirements for hydrogeological and engineering geological research work

1. Requirements for hydrogeological research

a) Hydrogeological research must clarify the degree of flooding of the mine, identify possible water sources flowing into the mining works. Additionally, it is necessary to evaluate water sources that can be used for domestic and technical purposes;

b) If there are operating mining sites in the area with similar hydrogeological conditions to the area under investigation, data on the degree of flooding, engineering geological conditions, and drainage measures applied at these mining sites must be utilized.

2. Requirements for engineering geological research

Engineering geological research must clearly define the physical-mechanical properties of clay rock, overburden rock above it, and other technical conditions related to mine design.

Article 24. Requirements for assessing pollution levels and environmental impact

1. Data on natural geography and environmental geology must be collected to forecast and evaluate key factors affecting the environment.

2. Geological hazards and negative impacts on the environment caused by clay quarry exploration activities must be assessed, and preventive and mitigation measures implemented. The content and level of environmental impact assessment must be included in the exploration plan.

Article 25. Requirements for researching technical conditions for mine exploitation

1. Preliminary boundaries of the open-pit, slope angle of the seam, final bench slope angle, stripping ratio, volume of overburden, and location of waste disposal areas must be determined.

2. Areas without industrial clay rock for construction of production facilities and residential areas, waste disposal sites must be identified; measures to protect underground space, prevent environmental contamination, and land reclamation must be proposed. To address land reclamation issues, soil layer thickness must be determined, agricultural studies conducted, toxicity of rock evaluated, and vegetation development potential assessed.

Article 26. Work on Calculating Reserves and Clay Mineral Resources

1. The calculation of reserves and clay mineral resources must be based on the reserve calculation criteria recognized by the Mineral Reserve Evaluation Council for each specific mine or according to the requirements of the investor, but must ensure compliance with technical standards. In the reserve calculation criteria, it must clearly specify the scope of use, basic quality requirements for raw materials, and technical conditions for mining.

2. The calculated reserve is the current reserve underground, not including losses during extraction. The unit of measurement for reserves is thousand cubic meters for raw clay for bricks and tiles, and thousand tons for raw clay for cement and other uses.³ For raw clay for bricks and tiles, the unit of measurement is thousand cubic meters, while for raw clay for cement and other uses, it is thousand tons.

3. In addition to reserves and clay mineral resources, the volume of overburden and the volume of rocks that do not meet the criteria within the scope of reserve calculation must also be calculated.

4. Reserves and clay mineral resources are calculated based on the scale and topographical characteristics using a topographic map at a scale of 1:1,000 to 1:5,000. Depending on the specific geological features of the mine, methods such as vertical cross-sections, geological block method, polygon method, and other methods can be used to calculate reserves and resources.

Article 27. Requirements for the Highest Reserve Level and Proportions of Reserve Levels

1. Requirements for the highest reserve grade

a) For mines in Group I and II, the highest level of reserve to be explored is the 121 level reserve;

b) For mines in Group III, the highest level of reserve to be explored is the 122 level reserve.

2. Requirements for the ratio of reserve grades

The quantity and reasonable proportion between the 121 and 122 levels of reserves shall be determined by the investor based on the geological characteristics of the mine, financial capacity, technical conditions for mining, and designed mining capacity, but must ensure that the ratio of 121 level reserves to the total of 121 and 122 level reserves is not less than 10%, and this must be reflected in the exploration plan.

Article 28. Content and Presentation Form of Documents in Exploration Reports for Clay Mines

The content and presentation form of documents in exploration reports for clay mines shall be carried out in accordance with the provisions on the procedures, formalities, review, examination, and approval of mineral reserves in exploration reports issued together with Decision No. 14/2006/QĐ-BTNMT dated September 8, 2006, of the Minister of Natural Resources and Environment.

Chapter 5.

IMPLEMENTING PROVISIONS

Article 29. Conversion of Reserve and Resource Levels of Clay

1. The reserve and resource levels of clay divided according to the regulations stipulated in the Usage Regulations for Classification of Clay Mine Reserves issued pursuant to Decision No. 28/QĐHĐ dated December 21, 1978, of the Chairman of the Mineral Reserve Review Council, must be converted to the reserve and resource levels as prescribed in this Circular.

2. The work of conversion and preparation of reports on the results of converting reserve and resource levels of clay shall be carried out in accordance with the Provisions on Classification of Solid Mineral Reserves and Resources issued together with Decision No. 06/2006/QĐ-BTNMT dated June 7, 2006, of the Minister of Natural Resources and Environment.

Article 30. Effectiveness and Responsibility for Enforcement

1. This Circular takes effect from January 1, 2010.

This Circular replaces the Usage Regulations for Classification of Clay Mine Reserves issued together with Decision No. 28/QĐHĐ dated December 21, 1978, of the Chairman of the Mineral Reserve Review Council.

2. The Office of the Mineral Reserve Evaluation Council is responsible for organizing monitoring, guidance, and inspection of the implementation of this Circular.

3. During the implementation of this Circular, if difficulties or obstacles arise, relevant ministries, sectors, localities, organizations, and individuals shall promptly report to the Ministry of Natural Resources and Environment for consideration and resolution.