Quartz Alloy
2011
How much pure gold are there in the specimen?
I have this really hard question for minerology. Here is the question: A specimen of rich gold ore weights 309.3g and its volume is 82,9 cc; quartz (G=2.65) is the only gangue mineral. The alloy contains 12.1% silver, the density of the alloy being 17.5 g/cc. How much pure gold are there in the specimen?
The question contradicts itself, as it states that quartz is the only gangue mineral in your gold ore, yet there is silver present. Therefore there must be either a silver mineral or an amount of electrum (Au-Ag alloy) present.
I will assume that your alloy is a mixture of only Ag at 12.1% and Au at 87.9%, and that we are dealing with g on the earth’s surface. Ag has an SG of 17.5 and Au has an SG of 19.3, and the density of the alloy (given) is 17.5 g/cc which is equivalent to an SG of 17.5 on the earth’s surface.
The first thing we need to do is calculate the density of the specimen:
Density=mass/volume
D=309.3g/82.9 cc
D=3.73 g/cc
Quartz has a density of 2.65 g/cc (given), so we have an excess densisity of:
3.73-2.65=1.08 g/cc
Therefore you have 1.08 x 82.9 cc of the total volume is alloy, or 89.5 g of alloy. 87.9% of the alloy is gold (given), so you have 89.5g x 87.9% = 78.7 g of pure gold.
CarPro C.Quartz Ceramic Quartz Coating on Alloy Wheel (Part 4)
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