Sampling and Analysis of Alluvial Gold Ore Deposits

In the last article, we introduced ‘Alluvial Gold Ore Grade and Exploration‘.
The topic I want to share with you today is ‘Sampling and Analysis of Alluvial Gold Ore Deposits’. It is about the washing of alluvial gold samples and the analysis of heavy sand of ALLUVIAL GOLD ORE DEPOSITS.


Alluvial gold samples should normally be washed at the sampling site. The work of washing should be performed by washing workers who have passed the training and examination. The washing must be carried out in a container capable of recovering the tailings. The tailings should be washed repeatedly until the naked eye observation no gold so far. The heavy sand from each wash was combined into one basic sample. Alluvial gold samples, gold particle size and gold fineness analysis samples taken in well exploration engineering can be washed repeatedly by SLUICE BOX or mineral jig.

placer gold sluice box
alluvial gold sluice box

In order to check the washing quality, it is necessary to wash 10% of the basic samples containing gold in the deposit. Panning inspection takes the panning tailings as the object. The washing coefficient is calculated according to the inspection results to explain the washing quality. Generally, the washing coefficient is not greater than 1.02.

Washing coefficient = (gold content of basic sample + check gold content of washing)/gold content of basic sample.



Heavy sand analysis includes:

  1. Single analysis of alluvial gold.
    The quality requirements for single analysis shall be:
    (1) Heavy sand separation and selection process reasonable, accurate and timely. More than two gold grains equivalent to 0.1 mm shall not be omitted.
    (2) identification (pick gold) should not omit the equivalent of 0.1 mm of more than two gold grains.
    (3) Gold weighing must use the balance accuracy in 1/100 thousand above.
    (4) Quality inspection.
  2. Multiple analysis. To understand the content of associated heavy minerals. Only partial samples are selected from the orebody.
  3. Combination analysis. Combine to scale from a single sample. To understand the content of the associated heavy minerals.
  4. Complete analysis. Grouped by layer. One to two pieces per layer for understanding heavy mineral assemblages.

Internal inspection: separation and identification (gold picking) internal inspection is 15% of the total amount of each batch of samples. The weight is 20% of the total number of gold-containing samples, and the qualified rate is 90%. If the qualified rate is between 60-90%, in addition to correcting the unqualified samples, the uninspected samples with the percentage of out-of-tolerance samples shall be supplemented. If the qualified rate is less than 60%, the whole batch shall be reworked. Gold particles found during separation and identification (gold picking) were incorporated into the original samples.

External inspection: separation and identification (gold picking) external inspection is 3-5% of the total number of samples. The external weighing test should be 5-10% of the total number of gold-containing samples. Some of them are qualified samples for internal inspection and used to check the systematic error of the balance. The other part is selected from untested samples to check for accidental errors in weighing. The pass rate is 80%. If the pass rate is 60-80%, the treatment method is the same as internal inspection. If the qualified rate is less than 60% or the balance has a large systematic error, all the samples shall be sent to the external inspection unit for reinspection. Identify causes and participate in reserve calculation with correct results.

If you have any comments or Suggestions, please feel free to leave a comment below or contact me directly.

The next post I will share with you is ‘Mining of Alluvial Gold Ore Deposits‘.

Workshop- Gongyi Forui Machinery Factory
Workshop- Gongyi Forui Machinery Factory

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  1. Dear Mr Asa,

    Thank you for the valuable information.
    I am an amateur, new to Gold mining with no enough knowledge & experience.
    I want to go into Alluvial -Placer Gold Mining
    I have a local Geologist advising me.
    But, still, I want to do Ore Mineral laboratory test to be sure that this site
    has good economical deposit
    Project location: Africa
    I would appreciate your advise
    Many thanks

Geology Here