Given SBMI’s commitment to transparency Management believes a lengthy description of its QA/QC process in its assay lab is necessary. This process is followed by SBMI personnel on all samples analyzed by SBMI’s assay lab near Globe, Arizona.

 

1.  All parts of the lab are inspected for any remaining contamination from prior runs.

2. The entire new sample is processed through the Lab Jaw Crusher.

3. The partially crushed sample in its entirety is processed through the Lab Hammer Mill.

4. The entire sample is split through the Splitter Box until an aliquot of approximately 100 to 125 grams is obtained. The aliquot is sent to the Lab Pulverizer, and the remaining sample is be stored in either a 1-gallon freezer bag or a 5-gallon bucket.

5. The Lab Pulverizer pulverizes the 100 to 125 grams aliquot down to a fine powder.

6. The pulverized aliquot is then placed on a small rubber mat and thoroughly mixed from side-to-side. At the conclusion of this mixing process, the aliquot is coned up so that the aliquot can be weighed. For individual assays, a full-assay ton of 29.16 grams from the aliquot can be used or a ½-assay ton of 14.58 grams can be used. To collect either portion from the aliquot cone, small amounts are continuously taken from opposite quarters of the cone.

7. The 14.58 grams (1/2-assay ton) or the 29.16 grams (full-assay ton) is then mixed with a flux and flour combination on another small rubber mat. The flux contains a mixture of soda ash, litharge (PbO) and borax. After all of the ingredients have been thoroughly mixed, the entire recipe is dumped into a crucible for melting in an electric furnace at 1,850 degrees Fahrenheit.

8. A minimum of 2 large tablespoons of the remaining aliquot on the first rubber mat is then dumped into a small brown envelope. The date and the sample name is written on the outside of the envelope so that the sample can be archived. A log of all archived samples is maintained.

9. The crucible with the recipe cooks for approximately a half an hour to 45 minutes. When the resulting melt is totally fluid, the melt is poured into a cast iron cake pan. The melt cools for 10 to 15 minutes until it solidifies.

10. Upon cooling, the poured melt is in the form of a metal button and slag. The slag can be discarded. The button is hammered until it is completely cleaned up and squared off. When it is subsequently weighed, the weight should be between 24 to 26 grams for full-assay ton assays or 14 to 16 grams for 1/2-assay ton assays. Any extreme deviations from this would indicate that the pulverized aliquot would need to be re-assayed with modifications to the flux addition. This modification would be based purely on the assayer’s experience.

11. The metal button is essentially lead, but precious metals are encapsulated in the button. The lead needs to be eliminated to expose the precious metals that were present in the pulverized sample aliquot. A bone ash cupel is utilized to both absorb and eliminate the lead. The lead can be oxidized and collected on the side of the cupel, but the silver, gold, and other precious metals cannot. All precious metals form a dore, or bead, at the bottom of the cupel when the lead is gone. The temperature for the cupel step is usually between 1,600 and 1,650 degrees Fahrenheit. This cupel step usually takes approximately 45 minutes.

12. At this point, the dore, or bead, needs to be flattened and weighed. The scale used by SBMI is accurate to a ten-thousandth of a gram. SBMI’s dore bead weight results are generally reported in ounces/ton, with one ounce/ton equivalent to 1 microgram of bead weight.

13. The dore bead can be composed of not only silver but also gold and some other platinum group metals, such as platinum and palladium. For this reason, the bead needs to be parted to determine the weight of each constituent. For this step, a solution of 6 to 1 distilled water to nitric acid is utilized to dissolve the silver in the bead at approximately 175 degrees Fahrenheit. The gold in the dore bead is unaffected by this solution. If the remaining gold bead amount is just trace, then the original dore bead weight was almost 100% silver. If the gold bead is weighable, then the weight of this gold bead needs to be deducted from the original dore bead weight to determine the silver weight in the original dore bead.

14. Care should then be taken to ensure all equipment is thoroughly cleaned after use to ensure no contamination of future samples. The plates and the inside of the Pulverizer should be vacuumed and brushed.

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