Fire assay clay crucible is made of fire clay and proprietary additives and has an extremely long history in the gold business. Its use is referenced in historical texts that are more than 3000 years, which when you think about it, is no surprise really. A crucible is, in simple terms, a ceramic cup, that’s why it is also called “pots”.
A modern fire assay pot is not that far removed from those of the past with the exception of the additional science behind its composition. Modern crucibles are made for mineral and Geochem laboratories use rather than refining and so are required to be exacting in their specifications. What’s more they should be strong enough to withstand huge changes in temperature through multiple uses.
Decent has more than 20 years experiences in the industrial ceramic and refractory industry, including fire assay clay crucible.
Drill core samples (or others) are received at the laboratory, crushed, milled and dried in the oven. Samples are then separated into bags, tagged and weighed.
Next, the samples are prepared for the fusion process, which requires a reducing environment and so the samples are mixed with flux, a carbon source (coal dust) and litharge (PbO).
The samples are then placed into a fusion/ refractory crucible, ready to go into the furnace. The high tempareture (1000 – 1200°C) melts the sample while the flux fuses with the gangue (non-precious material) and the now liquid lead collects all the precious metals. The newly-formed Pb-Au-Ag-PGE concoction migrates to the bottom of the crucible due to its high density.
As cooled lead sample is then separated from the glass waste (slag) with a hammer, and placed in a porous bone ash (MgO) crucible, ready for the cupellation step.
The sample is then placed in a muffle furnace at around 1000°C. The lead oxidises with the aid of the inflowing air from the furnace muffle and then immediately melts and is absorbed into the crucible, leaving behind what is known as a precious metal prill.
The prill is then analysed for its precious metal content through dissolving it in aqua regia (a mixture of hydrochloric and nitric acid) and the concentrations determined by spectroscopic methods (AAS, ICPAES, ICPMS).
Eventual detection limits are in the region of parts per billion but accuracy is usually in the region of 3 -5% for this metallurgical analytical technique.
L.O.I(loss on ignition)
Precious Metal Analysis
Fire assay crucible
SiO2 + Al2O3
Automatic molding equipment
ISO 9001 SGS
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Wooden Case Dimension (mm)
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Liling Xing Tai Long Special Ceramic Co.,Ltd
Tel: +86 13975373343
Company address: Shentan Industrial Zone, Liling, Hunan, 412200