Pyrometallurgy: Roasting, Smelting, Refining & Electrowinning

Pyrometallurgy: Roasting, Smelting, Refining & Electrowinning

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gold extraction from fire-assay fusion in Quartzose Ore (4 replies and 1 comment)

C
clyde
6 years ago
clyde 6 years ago
Hello,

I'm a junior geologist and I have a few questions concerning the fire assay fusion that labs use to determine Au concentration.

If I have a gold ore associated with Quartz SiO2, since quartz's melting point is around 1700°C and the fire-assay can only go up to 1100°C, doesn't this lead to an incorrect concentration result?

Are the reagents use to increase the Au extraction from its other compounds?

Thank you very much,

Clyde.
F
Siddiquf
6 years ago
Siddiquf 6 years ago
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Fluxes, mainly lead oxide, added to the sample powder, bring down the melting point of the charge. Reductants, added to the charge along with fluxes result in production of molten lead which selectively dissolves free gold and other precious metals. However, Fire Assay is science as well as art. Suggest you Google 'fire assay' to learn variations on the above basic theme.

Y
Yves
6 years ago
Yves 6 years ago
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In fact the borax and the soda ash in the flux is forming a borosilicate glass (like ordinary glass) with the quartz which melt around 650 deg C.

R
Richard S
6 years ago
Richard S 6 years ago
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I agree with the above replies,  The fluxes reduce the total mixture to be molten at lower temperature than silica alone.  Fire assay was developed to be very effective for recovering gold from silicate ores.  The presence of sulfides which might also contain gold requires some additional fluxes at times and methods have been developed.

http://www.kuntermetallurgy.com/

F
Siddiquf
6 years ago

If gold is trapped inside sulphides, for example pyrite, roasting the ore sample.at +600 degrees C, followed by Fire Assay can give a correct result.

g
giom
6 years ago
giom 6 years ago
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fire assay dosnt give the best result .if you have mecroscopic gold .wont even desolve at 1700 c .

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