Frequently Asked Questions:
Q - - -How large a sample do you need for testing?
A - - - We can run multiple tests on:
Q - - -Wet assays from other labs report gold but fire assays from different labs shown none; how can this happen? Are wet assays better?
A - - - Common problems include "nugget effect" in which a few, poorly disseminated particles of gold per pound of sample may produce both blank results and also highly elevated gold results from the same sample. Large samples used for fire assaying help reduce nugget effects, while small samples for instrument analysis tend to increase nugget effect error. We prefer fire assays.
Q - - - My concentrates show some good values but the raw ore shows nothing, why is this?
A- - - Prospectors are sometimes disappointed when they discover the concentrates look promising but the raw mineral shows little or no precious metal. One reason for this situation might be that concentrating a sample elevates the level of precious metals many times greater than raw mineral, so the concentrated metals exceed the threshold of detection, while the raw mineral may contain amounts of metal too small to be detected. Another possible reason is that the mineral taken for concentration possibly covered more ground or may have included richer material than the follow-up sample of raw mineral.
Q - - - I have several reports that show gold in the sample, but most reports do not; we have been told that we need secret processes to recover our gold. Is this true and if so, why?
A- - - Your question has different aspects. First, several conventional methods are available to assay for gold but the best one is fire assay. Spectrometers and other instrumental methods depend on computers and software for detection, and are subject to occasional software errors on complex mineral samples. We recommend and use fire assay assay methods for precious metals.
To resolve variations in different fire assay reports, take an average of the assay results. There are various ways to do this. Some methods include or exclude highest and lowest results before averaging, or include sufficient barren mineral equal to the bulldozer width or sampling width, etc. In actual mining, a substantial amount of barren mineral is processed along with the ore, producing a lower result than a simple average of assay values might indicate.
Report variance is common for non-homogenous mineral samples. Report variances arise from a number of causes but often they exist because mineral composition can be very different even in a small area. Sampling error is a common source of bias. Sometimes the gold content of a sample may be limited to a few particles per pound of material. When that type of sample is crushed and pulverized, some sub-samples can be barren while others show good values. Some forms of Hematite, Galena, and other heavy metallic minerals in light matrix are often difficult to keep homogenized after sample preparation so that even minimal handling induces sufficient movement of heavier particles to begin settling.
Q- - -Our report shows Tellurium in the sample, so doesn't that automatically mean it also contains Gold?
A - - - No. Other metals such as, Antimony, Arsenic, Bismuth, Cadmium, Chromium, Copper, Gallium, Germanium, Gold, Hafnium, Lead, Manganese, Mercury, Nickel, Thallium, Zinc, Zirconium, can form tellurides.
Q- - -We have reports from the 1950's that show no Nickel on our property yet new assay reports indicate small amounts of Nickel, so which ones are correct?
A - - - There could be several reasons to explain this mystery. Analytical instruments evolve and sensitivity has improved over the past 50 years, making it possible today to routinely detect amounts below 10 parts per million for many elements, which results in detection of more elements than older equipment. Water seepage and wind move minerals, along with rock slides, and more commonly, human activity in mining and sampling, all of which can render old assay reports useless for evaluating a mineral property. Heavy mining activity could render assay reports obsolete within days or weeks. Depending on the magnitude of events occuring on the property, an assay report older than a few years is probably no longer useful. Old assay reports have sentimental value but usually have little relevance to the present condition of a mine.
Q - - -What kind of tests, other than fire assays, can be done for gold?
A - - - We only recommend one method - fire assay. There are many other methods: Fire assay, ICP spectrometer, X-ray spectrometer, Atomic Absorption spectrometer, Neutron Activation Analysis and spectrophotometry by wet chemistry. Fire assays remain one of the most reliable direct methods of Au. determination. Fire assays actually refine and recover Au. and Ag., a direct method of visual confirmation of detected Au. and Ag. that can be physically weighed. There are so many advantages to this very effective method that it is preferred by most assayers for routine analysis of Au. in a wide variety of minerals. X-ray spectrometer is also reliable but is an indirect method and is subject to matrix variation error, absorption and enhancement effects, and peak overlap error, so it is generally not used without a preconcentration step first. The method is indirect because Au. particles need not be visible for the method to be successful. ICP is also an indirect method and may be subject to software error or interference from peak overlap, background subtraction error, and errors related to small sample size, incomplete acid digestions, and systemic errors such as "memory effect" from residual contamination which may bias the data, and a preconcentration step is usually necessary.
Each analytical method has advantages and disadvantages. Some clients use colorimetric wet chemistry test kits as a low cost alternative to test for gold and this is an indirect method which uses acid digestion plus an indicator solution to produce a color change in solution which suggests the detection of Au. Acids tend to dissolve many different elements, some of which must be removed or they may also produce a change in color in the solution and a false positive result. Interfering elements may be removed by precipitation and filtration through filter paper. If the colored solution follows Beer's Law, and no trace of interfering elements bleed through the filter paper used to remove them, the intensity of the colored solution may be inferred to result from the concentration of Au.; and if not, the method is subject to error. Filter paper pores often enlarge and leak due to extreme pH, temperature, or age of the paper, among other factors, and false positive results for gold with home test kits are common.
Q - - - How many samples should I test?
A - - - If you've never ordered an assay report before, send only one or two samples at first so you can judge what you will be receiving. As a general rule, risk and uncertainty are reduced by increasing the number of analyses, but risk is never zero. Even the most carefully researched projects retain to some degree all of the risks inherent in mining.
The best number of samples to take varies with initial assay data, the geology of mineral formation, the purpose of testing, budget or time constraints, etc., but the number of samples should be sufficient to have some confidence in relating the test results to the area sampled. Extreme sampling error can result from taking too few samples from a wide area, and taking samples exclusively from a small ore pocket or vein produces results not reproducible during actual mining of vein and waste mineral together.
Testing a few rocks may help identify mineral composition, but cannot provide enough data to conclude that the results represent a large area. If the tests are to attempt to confirm a specific discovery or small vein, geologists may often take a small number of samples in a limited area of mineralization per mining claim. For confirming large ore deposits covering many acres or multiple mining claims, geologists may specify a grid for sampling hundreds of samples with a specified number of drill holes. Drill core can be split vertically, with half sent for testing, and half retained for client records.
Sample selection can be done with as much scientific basis, or as little, as one's budget allows. Historically, most ore deposits were discovered by the individual prospector doing selective hand sampling of unusual mineralization.
Q - - -What is your turnaround for testing black sand concentrate?
A - - - Lab processing time varies by test and sample material, among other factors. Tests usually require 15 to 21 business days to process from the date we receive the order. Wet or damp minerals, unusually complex samples, non-mineral samples, and orders omitting payment or instructions usually take longer to process. Samples containing multiple, high-value elements are very complex and are not suitable for quick analysis.
Q - - - I have 200 pounds of black sand, who buys this material?
A - - - We know of no market for small amounts of mineral other than possibly a rock shop. You might find a buyer in the International California Mining Journal or other mining magazine, but most buyers have a minimum quantity which differs between different buyers.
Q - - - I want to know whether the minerals I have found contain diamonds or not. Can you help me?
A - - - No, we analyze minerals for metal content only. Gem examination requires different expertise and equipment. You might try The Gemological Institute , Carlsbad, CA (1-800-421-7250) to arrange for them to examine suspected gems or for additional information regarding testing.
Q - - - Do you identify the diatoms in soil?
A - - - No. We report metallic elements in soil samples. Product testing labs may have the equipment for identifying diatomaceous earth or clays which may require physical tests along with microscopic and chemical analysis.
Q - - - Do you examine properties and take samples for assays?
A - - - No. We only test samples submitted by clients. We never visit properties or select samples.
Q - - - Do you identify minerals in the soil?
A - - - We report metallic elements which the sample contains, but we do not report the mineral name or species. Sometimes a mineral species is obvious from the elements it contains, but the majority of geologic samples we receive are a mixed bag of many different types of mineral particles - i.e. 2% Magnetite, 6% Hematite, .07% Arsenopyrite, .001% Monazite, 1.6% Calcite, 23% quartz, etc., which would add greatly to the cost if each particle had to be separately identified and quantitated. We report the elements contained in the sample, such as Copper, Lead, or Zinc, which is specific information, rather than provide an opinion as to whether the probable identity is Chalcocite, Galena, or Sphalerite. A typical rock sample may contain various amounts of many different minerals.
Q - - - Do you test non-mineral particles (e.g. phytoliths, seeds, paint, glass)?
A - - - We accept soil samples for analysis but not individual microscopic grains or particles, fossils, seeds, plants, grasses, paint, or glass.
Q - - - Do you use soil maps in your analysis?
A - - - No. The origin of the sample may be of historic interest but is not a substitute for a chemical analysis of the specific mineral sample submitted.
Q - - - I want to know whether I have found a meteorite or not. Can you help me?
A - - - We can report metallic elements in a sample but we do not identify meteorites. Our test methods are destructive to samples, which must be pulverized. Meteorites have value only if they are intact. There are numerous organizations to help you. For example, you may contact the New England Meteorical Services - (508-478-4020) about testing.
Q - - -I'm sending some samples for a friend, so could you place his name on the reports?
A - - - No, for a number of reasons, our reports are only sent to the name and address of the person submitting the samples. If the addressee is unknown to the post office, the reports may not be delivered by them.
Q - - - I have several pounds of rocks containing at least 70% of gold and need to know where to send them to have the gold extracted. Might you be able to assist me here?
A - - - There may be someone interested in refining a few pounds of rocks, but most refiners require more than that. A rock that is 70% gold probably should not be refined at all, but would be sold intact as a specimen as it would be very rare.
Q - - -How long does an assay report remain valid? Will your report be accepted by a buyer as proof of value?
A - - -Just as each party to a real estate purchase should have their own lawyers to advise them, each party to a purchase or investment in a mine should do their own sampling and retain their own independent assayers. Assay reports are not transferable to other mining claims or group of claims, or to other people. One sample and one assay report does not represent the entire mining claim. Small ore deposits can be depleted by repeated sampling or limited ore removal, making assay reports inaccurate within a short time - possibly as soon as a few weeks after the report date. New lab reports should be preferred over old lab reports made several years ago.
Q - - -Can you include a full description of the methods, procedures, and technologies used in my assay?
A - - - We only report basic data obtained by analysis in either ppm, oz/ton, or percent, in a printed report similar to printed reports supplied by other assayers for work in the same general price range. Our listed prices DO NOT include full, formal reports describing the sample appearance, chain of custody documentation, methods and procedures used, instrumentation and graphs, technology, proprietary methods, references to literature, flow sheets for mineral processing, feasibility studies, names and addresses of buyers, or other information which would greatly increase the cost of analysis. We sometimes have clients request a formal report after our reports have been received, but we do not offer this service.
Q - - - I have platinum group in the form of a processed powder. It cannot be melted even with special melting fluxes and will not dissolve in any acids. Can you tell me everything that is in it?
A - - - No, probably not everything. We can identify 72 of the 92 naturally-occurring elements by spectrometer. The 20 elements we omit include most of the gases, carbon, boron, and a few others. Many minerals resist acid attack, which is one reason fire assaying (thermal fusion) is usually preferred for precious metal ores. Graphite, some refractory clays, carborundum, magnetite and chromite mineral, may resist both acid and thermal attack. Most minerals melt with thermal flux agents added if a proper ratio of sample to flux is reached and the sample is ground sufficiently fine. A mineral that is highly resistant to lab methods could be difficult and expensive to place into production and this may be a "red flag" that perhaps development may not be feasible.
Q - - -I have a (fill in the blank...atomic frequency detector, molecular discriminator detector, proton exciter, inductive aurimeter, etc.) and it shows gold 100% at great distances; why do assayers show no gold in my samples?
A - - - The detection method you describe isn't credible in our opinion. Gold doesn't emit anything that could be detected through hundreds of feet of soil and certainly not from miles away.
Q - - -I refine gold and cast pure metal objects and need an assay to reassure customers that my product is pure. How much metal do you need for a test?
A - - -It's not a good idea to be using a single assay report to certify the next 2 years of metal production. The source material often varies with every batch. Your situation requires an ongoing quality control program to test every new batch of metal, not a single assay of one batch. We analyze precious metal ingots and objects for some purposes, but not for quality control because that usually requires an on-site evaluation of the volume of metal produced and a statistically-accurate sampling program at your plant.
Q - - - Does your assay provide a recovery method needed to process my ore for precious metals?
A- - - No. The design of extraction processing or flow sheet for a mineral involves much more than assay of a few samples. Assays indicate the contents of the sample. A mining engineer, metallurgical engineer, or chemical engineer may provide that service.
Q - - -How should I select samples for testing?
A - - - Many prospectors want to:
These different goals suggest different ways of selecting a sample. A single test cannot accomplish everything.
If identification of a metallic vein is the purpose of testing, then you might select only the richest vein material to test elements it contains. The assay result cannot indicate the average ore grade but it does identify the metals present.
If the primary purpose for testing is to learn the average ore grade of the deposit available for mining, samples should be taken carefully in order to be as representative as possible of the ore deposit. This could involve the client taking many small samples from a larger area, blending them well, and selecting a portion to submit for assay. This sampling method offers a better average or percentage for a larger area. If the purpose of testing is to calculate ore grade or amount of metals available for mining, samples taken broadly across the ore body should include vein and waste rock equal to the expected mining width in order to be as representative as possible of the ore deposit.
Some prospectors simply want to know what elements are present in a colored spot on a rock or a tiny particle in the rock. If that is the goal, then we would need about 1 oz. of colored specks or particles or more for testing. We do not analyze a single tiny speck of color or a very small spot while it is still on a rock. Analysis of multiple elements often requires multiple methods for best results.
To identify elements contained only in the host mineral, you can separate and exclude the vein material from the sample of host rock. To identify elements contained only in vein material, do the opposite - separate the vein material and exclude it from the host rock.
If the purpose is to identify only the vein or visible metallics, samples could be taken narrowly at the richest part of the vein for testing, selecting only the rich vein material for testing while excluding the host rock from the sample. A sketch of the area can record the points sampled, by sample number.
Q - - -How should I prepare samples?
A - - - Mineral samples must be dry, and may be rocks, sand, soil, mineral powder or a mixture of these. We include sample preparation sufficient for our use at no extra cost, except there may be additional charge for samples that are damp, wet, hygroscopic, or large rocks over 2" in size.
Wet or damp samples should be air-dried first before shipping to us. If the soil forms clumps or sticks to the side of the container, it is probably too wet for testing. If wet clay is sent for testing, add 10 additional days to lab turnaround for air drying.
Clients can prepare their samples as long as the sample is received as dry -100 mesh mineral powder which we consider adequate for all tests. Wet samples may result in additional charge for drying as our mill requires relatively dry mineral.
Non-geologic materials for which we have no calibration standards may be submitted for qualitative analysis in which elements detected are reported along with their relative intensities rather than percentages.
It's always a good practice to retain some of the sample that you are shipping for testing in case you may want additional tests done later on, or merely for your own records.
Q - - - Which type of test is the best one for my ore?
A - - - The elements and amount sought may determine the preferred test method. Platinum group metals are assayed separately using a series of different methods such as fire assays and spectrometer finish. Every test method involves some degree of compromise in accuracy vs. number of elements analyzed, detection limits vs. lab processing time, among other factors.
A few mineral species are practically acid-insoluble. For most elements, Aluminum through Zirconium, we use an xray spectrometer and atomic emission plasma-arc spectrograph for multi-element analysis reporting concentrations as percentages. These methods allow analysis of samples of dry powdered mineral without prior acid digestion. This avoids problems of mineral solubility in acids. The tradeoff is that dry powder methods offer less accuracy. Wet instrumental methods such as AA and ICP provide greater accuracy for soluble minerals but the tradeoff is that these methods require that minerals dissolve in acids or be fused with fluxes. Minerals that do not dissolve completely in acids or fuse easily can produce reports that occasionally vary from lab to lab, depending on the degree of success they had in dissolving the mineral sample, among other factors.
We assay gold & silver minerals by fire assay, reporting troy oz. per ton. There are other satisfactory methods but we prefer the reliability of larger test samples using the fire assay method. The fire assay with a 30 gram sample, provides a 60 times larger test sample than AA or ICP methods using 0.5 grams.
Geologists usually order test code S3, a multi-element analysis, which includes a gold and silver fire assay. This combination is designed to identify multi-element ores. If heavy metals are suspected, additional assays for PGE (Platinum Group Elements) are often ordered which are also reported in troy oz. per ton.
If only trace amounts (pathfinder elements) are sought, then test methods having extreme sensitivity may be the most economical choice. Other labs which use ICP-MS (mass spectrometers) may be able to accurately report below 100 ppb but contamination levels from sample processing machinery (crushers, pulverizers, etc.) are often much higher than this amount.
Our mineral tests are designed for exploration and prospecting purposes and not ore sales, mining promotion, or investment offerings because third parties should independently select their own samples and assayers. We do not provide on-site testing. Low cost semiquantitative multi-element tests should not used to value large commercial transactions. For transactional purposes, quantitive assays are run in duplicate or triplicate with proof assays for best results and the bulk mineral tested should be held in secure, bonded storage during testing and until the transaction has been completed. On-site samplers and assayers, such as Alex Stewart Ltd. are customarily employed for these transactions.
Q - - -I'm thinking of investing in a mining project and they're showing me a few assay reports indicating some gold values. Is this enough information for me to invest a large sum in the project?
A - - - No, absolutely not. Lab reports are raw data and not a final conclusion that a sufficient discovery has been made for investment or mining purposes. Never make any investment decision without first seeing the engineering data. A few lab reports are no substitute for extensive sampling and a registered mining engineer’s report.
What if the mining promoter had dozens of undisclosed assay reports showing no gold on the property? A promoter asking prospective investors for money based on a few assay reports may be an early sign of fraud. However, you need far more information than assay reports before committing to a mining deal. You should have a mining engineer examine the property and then consult a mining attorney for advice before investing. Samples should also be taken by the investor or his geologist for independent assay and confirmation of values.
If you are new to mining, please read the paragraph below very carefully.
State registration of a stock offering does not reduce mining risk and offers no protection against investor fraud. Greater disclosure does not necessarily equal less risk. Investors are always better off investing in industries where they are knowlegeable and familiar.
Verify the legitimacy of the securities seller. Mining stock is sold by licensed dealers. Legitimate mining companies usually do not solicit investors by telephone or mail or ask for unsecured investments. As part of your due diligence, it's advisable to have your attorney investigate the civil and criminal records of the mining promoter before you invest in a private offering of mining stock.
Make sure the mining firm is registered with the city, county, state and federal agencies as required by law. If shares of stock in a mining project are offered to private investors, the shares must be registered with the state prior to the private offering with few exceptions. Some states consider "partnership shares" to be "securities" which must be registered. If mining claims are divided to be sold, the division may have to first comply with land subdivision map laws. In addition, have a mining attorney investigate to see if the mine is actually owned by the mining firm, obtained the necessary legal permits to mine including filing environmental restoration plans, proper zoning, and has employed personnel with extensive experience in mining the particular metal sought.
Don't buy "gold in water", "colloidial gold", "micron gold", "unassayable gold" or variations of this theme that are a waste of time and money. Processes used by mining companies to extract precious metals are well known. "New", "secret", or "untested" processes are a red flag for investors. There are low cost processes already available for gold recovery.
Measure the potential reward against the actual risk. Mining is a capital-intensive industry that potentially offers great rewards. However, mining ventures are extremely high-risk, and investments are usually long-term. Therefore, be skeptical of "guaranteed" high returns over a short period of time.
Larger mining companies are usually willing to finance or develop a highly profitable project. If a mining promoter turns to the general public or investors unfamiliar with mining risks to raise money, that alone may be a red flag warning that the property may have previously been rejected by experts. Small, rich veins and ore pockets are commonly found and may not be enough to make profitable mine.
To attract investors, mining promoters have occasionally altered, forged, or selectively disclosed assay reports or highgraded or salted test samples. Bre-X is worth remembering because it shows that even listed companies with expertise and world-class assayers can become a victim of fraud. Assay reports alone are not "due diligence" and should never be used alone to persuade potential investors. Assay reports are raw data which may suggest indications of value but do not establish a mine.
Geologists and mining engineers evaluate the size and grade of the ore deposit, costs and feasibility of production, which, along with assay results, may provide a basis for estimating the value of the mining project. Limited test results should be regarded with caution as they may not be duplicated in larger scale tests and should NEVER result in promotional activity without substantial assurance that the project can be profitable.
