1.5 Sample collection, washing (processing), and heavy sand (chemical) analysis
1.5.1 Sample Collection
1.5.1.1 Trench exploration should be carried out to a depth of 0.3m in weathered bedrock, and groove sampling should be conducted. The cross-section of the sample groove should not be less than 0.2m × 0.1m, sample length should not exceed 1m
1.5.1.2 Drilling requires continuous segmented and layered sampling from the hole mouth to the hole bottom. Sampling length of precious metal placer: The mud and sand layer shall not exceed 1m, and the sampling length shall be 0.2m~0.5m when approaching or within the sand layer. When it is confirmed that the mud and sand layer does not contain minerals, sampling may not be required: tin ore, rare metal sand ore, and rare ore sand ore, with a sampling length of 0.3m~1.0m. When it is close to weathered bedrock or difficult to drill, the sampling length can be reduced.
1.5.1.3 During well exploration, samples should be collected continuously in sections and layers. If the exploration is mainly carried out with flat bunkers, continuous sampling should be taken when excavating in the sand ore layer. To reveal the thickness of the sand ore layer, raise and/or blind wells should be excavated at the corresponding engineering spacing of the exploration type, and samples should be collected in sections and layers. The sampling method and specifications should be determined through experiments based on the characteristics of the deposit.
1.5.1.4 In rare metal placers, when the content of certain useful minerals is very low and it is difficult to detect or quantify using small sample heavy sand analysis or raw ore chemical analysis, it is necessary to take samples with a larger volume for heavy sand analysis. Samples should be taken separately according to different types of ore (stone), and different engineering samples of the same type should be combined to make them representative, with a sample size of 0.5t to several tons.
1.5.2 Sample washing
1.5.2.1 Washing must be carried out on-site. Served by trained and qualified washing workers.
1.5.2.2 It is required to elutriate the tailings in a container that can recover them. The tailings must be repeatedly elutriated until the last two observations of aimless and heavy minerals are made with the naked eye. The heavy sand obtained from each washing is combined into the basic sample.
1.5.2.3 The samples of the well exploration project can be repeatedly sorted by a chute or jig to obtain the concentrate, until the last two macroscopic observations of aimless and heavy minerals are made.
1.5.2.4 Quality inspection of washing should be carried out on 10% of the tailings from the basic sample of the deposit. Calculate the washing coefficient based on the inspection results, and the requirement for precious metals is not greater than 1.02.
Elutriation coefficient basic sample target mineral quality inspection target mineral quality basic sample target mineral quality
1.5.3 Heavy Sand Analysis
1.5.3.1 Heavy sand analysis must be undertaken by testing units that have obtained national or provincial-level qualifications and certification from metrology departments, ranging from Level 3 to Level 1.
1.5.3.2 Heavy sand analysis items:
a) Single item analysis of target minerals to accurately determine the content of target minerals:
b) Multiple analyses, selecting some samples from the ore body to understand the content of associated useful heavy minerals;
c) Combination analysis, combining in proportion from individual samples to understand the content of associated useful heavy minerals; d) Full analysis, combined by layers, with one to two pieces per layer, used to study heavy mineral combinations.
1.5.3.3 The quality requirements for the separation of heavy sand minerals can be found in Appendix C, where the quality requirements for single analysis of precious metals are as follows:
a) The heavy sand separation and selection process is reasonable, and no more than two precious metals equivalent to 0.1mm should be missed; b) Heavy sand identification (picking precious metals) shall not miss more than two precious metals equivalent to 0.1mm; c) Precious metal weighing requires the use of a balance with an accuracy of over 1/100000.
1.5.3.4 Quality inspection and handling of internal and external inspection results:
a) Internal inspection: Internal inspection samples should be extracted in stages and batches, while also taking into account the representativeness of engineering distribution and mineral sample distribution. Geological personnel will extract from the duplicate samples, encode them, and send them to the original experimental testing unit for internal inspection. The internal inspection sample of non precious metal minerals is 10% of the total number of samples. Sampling ratio of precious metals: 15% of the total number of samples in each batch are separated and identified (selecting precious metals), and 20% of the total number of target minerals are weighed for internal inspection samples. The qualification rate is required to be ≥ 90%. If the pass rate is between 10% and 90%, in addition to correcting the unqualified samples, the percentage of unqualified samples that exceed the standard will be retested. If the pass rate is less than 10%, the entire batch will be reworked. Merge precious metals found during internal inspection during separation and identification (picking precious metals) into the original sample;
b) External inspection: The external inspection samples are selected from the original experimental testing unit and entrusted to a higher-level testing unit. Non precious metal minerals account for 3% to 5% of the total sample size. Ratio of external inspection for precious metals: Separation and identification (selecting precious metals) samples are 3% to 5% of the total number of samples containing target minerals, and weighing samples are 5% to 10% of the total number of samples containing target minerals. Some of the samples are qualified for internal inspection to verify the systematic error of the balance. The other part is selected from samples that have not undergone internal inspection to check for accidental errors in the balance. The qualification rate is 80%, and when the qualification rate is between 60% and 80%, the processing method is the same as for internal inspection. When the qualification rate is less than 60% or there is significant systematic error in the balance, all samples shall be sent to the external inspection unit for re inspection to identify the reasons and participate in the estimation of mineral resources/reserves with correct results. The allowance for accidental errors in weighing precious metals is twice the inductive capacity of the balance.
1.5.4 Chemical analysis of raw ore
When residual sand ore, slope sand ore, and target mineral particles are too fine or contain too large clay to be washed or elutriated, chemical analysis should be conducted on the samples.
1.5.4.2 The sample processing must go through procedures such as drying, crushing, and grading, and the grading can be processed according to Q=Kd2. It can also be processed to 1mm before grading.
In the formula: Q - mass of the sample after reduction (kg); K-reduction coefficient:
D - Maximum particle diameter after sample crushing (mm).
The K value is an empirical value: the K value of precious metals increases with the increase of particle size, with commonly used values ranging from 0.4 to 1.0; Tin is 0.2~0.3; 0.1~0.3 for rare metals; Rare earth metals range from 0.2 to 0.5.
1.5.4.3 Chemical analysis:
a) Basic analysis:
1) Tin: A deposit mainly composed of cassiterite. When the tin content of cassiterite in the ore sand exceeds 90%, the analysis of total tin can be used as the basis for delineating the ore body. When there is high colloidal tin or sulfide tin, the grade of tin in the cassiterite in the sample should be determined as the basis for delineating the ore body;
2) Ilmenite, rutile: TiO,:
3) Precious metals: metallic elements;
4) Rare metals, rare earth metals: analysis of metal oxides; b) Chemical analysis quality:
1) Sample testing must be undertaken by testing units at the third to first level that have obtained national or provincial qualifications and certification from metrology departments:
2) Internal inspection: The results of basic analysis, combination analysis, and phase analysis should be subjected to internal inspection in batches and stages. The internal inspection samples should be selected by geological personnel from the secondary samples, accounting for 10% of the total number of original analysis samples. They should be coded and sent to the original analysis laboratory for analysis, with a pass rate of 80%;
3) External inspection: Samples shall be extracted from the original laboratory based on 5% of the total number of original analysis samples. The total number of external inspection samples shall not be less than 30, and the qualification rate of external inspection shall be 80%;
4) The methods for handling chemical analysis quality and internal and external inspection analysis errors shall comply with DZ0130.3-94 "Quality Requirements and Inspection Methods for Rock and Mineral Analysis". The formula for calculating the allowable error of ore analysis is as follows:
In the formula: y - Calculate the relative double difference (%); C - correction coefficient; X - Determination result value (%).
The correction coefficient Sn (sand ore) is 1.00, and Sn is 1.50; WO, (sand ore) is 1.50; 1.00 for rutile (placer); 1.00 for ilmenite (placer); The values of precious metals Au, Ir, Rh, Os, Ru are 0.29, and Ag, Pt, and Pd are 0.40; Rare metals and rare metals Nb2O5, Ta2O5, BeO, ZrO2, HfO2, Ce2O3, and La2O3 are 0.67, while Li2O3, ZrO2 (placer), Rb2O, Cs2O, RE203, Y203, Yb2O3, SrO, and Se2O3 are 1.00.