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Fire Assay | Avantor

Fire Assay in the mining process

Fire assay is a method used to determine the concentration of precious metals in ores. The workflow involves sample preparation, fusion, cupellation, and measurement. Supplies required for fire assay include fluxes, crucibles, tongs, scorifiers, and furnaces. The method is accurate and widely used in the mining industry. The fire assay workflow and supplies can vary depending on the type of sample being analyzed and the desired level of sensitivity.

Avantor manufactures fire assay consumable items such as Cupels and crucibles, custom made flux, fluxing reagents including borax, soda ash, silica and litharge.
We offer the Mines Assay 3 electric fusion and cupellation furnace, as well as larger gas cupellation and fusion furnaces. We also offer a single head or dual head flux dispenser offering fast and safe delivery of your flux. Tumbler mixers are also available to ensure fast and efficient mixing of your sample with the flux.

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Fire Assay Supplies

Cupels are used for fire assay of precious metals. Available in a range of sizes.

Crucibles contain solutions to be dried for constant weight using extreme temperatures then to be ashed for minimizing weight. 

Scorifiers are for burn off impurities in samples (also called ashing) before the fire assay process

Small lead pellets with definite amount of silver which may be added to crucible before fusion or tapped into cleaned lead buttons before cupellation.

Pouring molds are used in the fire assay process to cool molten samples

Crayons are used for marking the crucibles before they go in the fire

Fire Assay Equipment

There are many applications for furnaces including ashing, cupel pre-heat, and concentrate drying or oxidation

Accessories for MAS furnaces including doors and trays

Replacement parts for MAS-3 Furnace including c-clamps, and elements

Refractory Cement is used for furnace maintenance or securing cupels or crucibles in place in the furnace

Furnace cap and Cupellation hoods are designed to capture the lead fumes from fusion or cupellation furnaces.

Workstation dust hoods are used where dust is created such as fluxing, cleaning pulverizer bowls or cleaning screens. 

Cupel and Crucible forks are designed to move samples in and out of high heat appliances.

The furnace scraper is for spreading bone ash and scraping spills from the furnace

The furnace scraper is for spreading bone ash and scraping spills from the furnace

The furnace shovel is ideal for either catching scrapings when cleaning the furnace or adding bone ash

Trays are ideal for carrying crucibles, cupels or buttons.

Available in single or dule head formats, flux dispensers enable users to prepare and dispense two different flux recipes simultaneously

Flux Ingredients

Available in single or dule head formats, flux dispensers enable users to prepare and dispense two different flux recipes simultaneously

Flour is a commonly used reducing agent in Fire Assay flux. It is used to reduce litharge to molten lead for the collection of precious metal in the sample.

Where appropriate Fluorspar is used in Fire Assay flux to improve fluidity of the slag by suspending any infusible particles.

Small lead pellets with definite amount of silver which may be added to crucible before fusion or tapped into cleaned lead buttons before cupellation.

Lead Foil is typically used in both Fire Assay bullion work and cupellation.  For example, to wrap bullion samples, or for additional cupellation purposes.

Litharge is produced from highly refined lead and offers a very low level of precious metal impurities.

Potassium Nitrate is used as an oxidizing agent during mineral fire assay and refining. 

Silica flour is added to samples to protect the crucible in the fusion phase of the Fire Assay process. Insufficient silica levels will result in increased and erratic crucible wear.

Silica sand is added to samples to protect the crucible in the fusion phase of the Fire Assay process. Insufficient silica levels will result in increased and erratic crucible wear.

Silver foil is added to sample/flux mixtures as an inquart agent facilitating the collection gold or silver in fire assay. 

Silver nitrate power is added to sample/flux mixtures as an inquart agent facilitating the collection gold or silver in fire assay.  

Silver sulfate power is added to sample/flux mixtures as an inquart agent facilitating the collection gold or silver in fire assay. 

Soda ash (sodium carbonate) is a basic component found in fire assay flux. In either light or dense format, it reacts with silica based minerals to form fusible sodium silicates.

Test Lead is used for analysis of precious metals in both fire assay bullion work and cupellation.

Fire Assay Tools

Ideal for flattening beads, anvils are constructed from shaft steel with a hardened surface.

Pliers are used for picking up small objects such as beads.

Bead and button hammers are ideal for flattening beads or deslagging buttons

Provide maximum personnel safety when transferring corrosive or extreme temperature-subjected samples by using laboratory tongs.

Forceps and tweezers are available with either straight or curved tips with a range of thickness for precise control.

Fire Assay Safety Apparel

Protect your face in high heat environments with aluminized or gold-plated face shields.

Gloves and hand protection for high heat application often used in mineral testing.

Body and foot protection needed for working with high heat equipment.

Certified Reference Materials

KLEN's CRMs are certified products containing a range of analytes including Au, Ag, Pt, and Pd at various ppm levels.

Rocklabs Gold Standards are reference materials that are certified for either Pt, Pd, Au or Ag.

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