Details

MINE SAMPLING NOTES

Theory

Mine sampling is a critical process in the mining industry, ensuring that the quality and quantity of mineral resources are accurately assessed. The primary objective is to obtain representative samples that provide reliable data for decision-making in exploration, development, and production.

 1. Purpose of Mine Sampling

• Resource Estimation: To determine the grade and volume of mineral deposits.
• Quality Control: To ensure consistency and quality of the ore extracted.
• Economic Evaluation: To assess the viability and profitability of mining operations.

2. Sampling Principles

• Representativeness: Samples must accurately reflect the material being sampled.
• Homogeneity: The degree to which the sample material is uniform.
• Randomness: Ensuring samples are taken in an unbiased manner.
• Reproducibility: The ability to obtain consistent results from repeated sampling.

3. Sample Preparation and Analysis

• Crushing and Grinding: Reducing sample size to a manageable level while ensuring representativeness.
• Splitting: Dividing samples into smaller, equally representative portions.
• Assaying: Chemical analysis to determine the content of specific elements or minerals.

4. Quality Assurance and Quality Control (QA/QC)

• Standard Operating Procedures (SOPs): Ensuring consistency in sampling processes.
• Duplicate Samples: Collecting and analyzing duplicate samples to check for consistency.
• Blanks and Standards: Using known reference materials to check for contamination and accuracy.

5. Challenges in Mine Sampling

• Heterogeneity of Ore Bodies: Variability in ore composition and distribution.
• Sampling Bias: Errors introduced by non-representative sampling techniques.
• Sample Contamination: Unintended inclusion of foreign materials affecting sample purity.

Method

1. Channel Sampling:

• Description: Involves cutting a groove or channel across a rock face, often in ore bodies.
• Procedure: A consistent, measured volume of material is removed from the channel, ensuring representative sampling.
• Applications: Suitable for stratified deposits and when accurate horizontal and vertical sampling is necessary.
• Advantages: Provides a continuous sample that can reveal variations in ore grade.
• Disadvantages: Labor-intensive and time-consumer

2. Chip Sampling:

• Description: Small pieces of rock or ore are chipped off a rock face at regular intervals.
• Procedure: Systematic collection of chips, usually from a grid or along a line.
• Applications: Used in exploration phases and where the rock face is irregular.
• Advantages: Quick and less labor-intensive than channel sampling.
• Disadvantages: Less accurate and may not be representative if not done systematically.

3. Grab Sampling:

• Description: Random collection of ore or rock fragments from a muck pile or surface exposure.
• Procedure: Ore fragments are collected without a systematic approach.
• Applications: Often used in early exploration stages or for quick checks.
• Advantages: Very quick and easy to perform.
• Disadvantages: Highly unreliable and non-representative.

4. Bulk Sampling:

• Description: Large volumes of material are collected to obtain a representative sample.
• Procedure: Large sample sizes, often several tons, are collected and then processed.
• Applications: Used to assess the ore grade and metallurgical properties on a larger scale.
• Advantages: Provides a more comprehensive understanding of the ore body.
• Disadvantages: Expensive, time-consuming, and requires substantial logistical support.

5. Diamond Drilling:

• Description: Core samples are extracted using a diamond-tipped drill.
• Procedure: A cylindrical core of rock is drilled out and brought to the surface for examination.
• Applications: Deep sampling and exploration, providing continuous cores for detailed analysis.
• Advantages: Offers a continuous sample that can be studied for geological features and ore grade.
• Disadvantages: Expensive and requires specialized equipment and personnel.

6. Reverse Circulation (RC) Drilling:

• Description: Uses a dual-walled drill pipe to bring rock cuttings to the surface.
• Procedure: Air is pumped down the outer pipe, and rock cuttings are brought up through the inner pipe.
• Applications: Exploration drilling where rapid and cost-effective sampling is required.
• Advantages: Faster and cheaper than diamond drilling, provides large volume samples.
• Disadvantages: Provides rock cuttings rather than intact cores, limiting geological detail.

7. Auger Sampling:

• Description: Uses a helical screw to bring soil and rock fragments to the surface.
• Procedure: Auger drills into the ground, lifting material to the surface.
• Applications: Suitable for shallow, soft, and unconsolidated deposits.
• Advantages: Quick and relatively inexpensive.
• Disadvantages: Limited depth and may not penetrate hard rock formations.

1. Definition and Purpose:

Mine sampling reductions involve the systematic process of reducing the volume of a sample while maintaining its representativeness for analysis. This process is crucial for efficient handling, analysis, and accurate estimation of ore quality and quantity.

2. Stages of Sample Reduction:

• Primary Sampling: Initial collection of a large, bulk sample from the mining site.
• Secondary Sampling: Further reduction of the primary sample to a manageable size for transportation and laboratory analysis.
• Tertiary Sampling: Fine-tuning the sample size to ensure it represents the entire bulk accurately.

3. Techniques:

• Coning and Quartering: The sample is poured into a cone, flattened, divided into quarters, and two opposite quarters are discarded. The remaining quarters are recombined and the process is repeated until the desired sample size is achieved.
• Riffle Splitting: The sample is passed through a riffle splitter, which divides it into equal parts, ensuring each part is representative of the whole.
• Rotary Splitting: The sample is fed into a rotating device that evenly distributes the material into multiple containers.

4. Importance:

• Accuracy: Ensures that the reduced sample accurately represents the bulk material.
• Efficiency: Reduces the amount of material that needs to be transported and analyzed.
• Cost-Effective: Minimizes laboratory costs by reducing the volume of material that needs detailed analysis.

5. Factors Affecting Sample Reduction:

• Sample Size: Larger initial samples may require more stages of reduction.
• Material Heterogeneity: Uniform materials are easier to reduce accurately than heterogeneous materials.
• Reduction Method: The chosen method must suit the material type and desired sample size.

6. Challenges:

• Bias: Improper sampling techniques can introduce bias, leading to inaccurate results.
• Contamination: Care must be taken to avoid contamination during the reduction process.
• Losses: Minimizing losses of fine particles is critical to maintain sample integrity.

8. Applications:

• Exploration: Helps in estimating the ore reserves and planning further exploration activities.
• Quality Control: Used in routine checks to monitor the quality of the extracted ore.
• Resource Estimation: Aids in the accurate calculation of the quantity and quality of mineable material.