Fire Assay Flashcards

Fire Assay Flashcards

Fire Assay

A branch of quantitative chemical analysis where metals are determined in ores and metallurgical products by extracting and weighing in metallic state.

Metals Determined by Fire Assay

Gold, silver, and platinum.

Gangue

The non-valuable minerals in ore.

Ores

Mineral aggregates from which one or more metals can be extracted at a profit.

Metallurgical Products

A large range of metal-bearing mixtures and compounds.

Concentrate

Grade (amount) of precise metal as compared to the waste material in a given quantity of ore or metallurgical product.

Flux

A chemical reagent which, when heated, combines with or takes into solution a difficultly fusible compound.

Slag

The liquid part resulting from fusion which contains the waste, gangue.

Dore

Product of cupellation that contains gold and silver (alloy of gold and silver).

Bullion

Gold and silver in lump or valued by weight.

Fine

Purity of gold measured per 1000 parts of gold bar.

Carat

Measure of fines (purity) of gold. Pure gold is described as 24 carat gold.

Preparation of ore sample

To be well mixed and pulverized.

Homogeneity for fire assay process

Achieved through crushing, pulverization to require size, thorough mixing and obtaining a representative sample.

Ultimate function of Slag Fusion

To separate the gold and silver alloy from the waste material.

Two liquids produced in fusion stage

Liquid lead containing the valuable minerals and liquid slag containing waste matter (gangue).

The effectiveness of fire assay to separate Au, Ag and base metals from ore depends on two properties.

Its weak affinity for non-metallic elements and its great affinity for molten lead.

The role of Lead in fire assay

Necessary for the collection of the precious metal.

Litharge (lead oxide, PbO)

Melts at 883 °C when it becomes a molten basic flux, it acts as an oxidizer and desulphurizer

Sodium carbonate (Na2CO3)

Melts at 825°C and combines with silica and alumina producing fusible silicates and aluminates.

Borax (Na2B4O7)

Melts at 742°C and it combines with or dissolves the basic and some of the acid constituents of the gauge,producing easily fusible complex borates and mixtures of borates.

Silica (SiO2)

Melts at 1755°C, combines with metallic oxides which in many cases is considered more fusible than itself.

Nitre-(KNO3)

Melts at 339° and it neutralizes the effects of an excess of reducing substances in material to be analysed.

Common salt (NaCI)

A neutral substance that melts at 819°C and sometimes used as a cover in fusion to exclude air.

Excess Acid Ore

High silica or alumina.

Excess Base Ore

High in sulfides or oxide.

Self Fluxing

Approximately equal amount of acidic and basic constituents.

Neutral Ores

Ores that have no power to reduce litharge (PbO) to metallic lead.

Oxidizing ores

Ores containing minerals that will oxidize lead back to litharge.

Reducing Ores

Those ore that contain reducing materials that will reduce lead oxide to metallic lead.

Cupellation

Process by which gold and silver are separated from lead from which they are alloyed.

Parting

Process of separating gold and silver from their alloy and is effected by means of nitric acid (HNO3).

Annealing

Heating the gold from parting process at about 650"C for about 10 minutes.

Most alloys on solidifying

Segregate to some extent, so that the cooled metal is never uniform in composition.

Flour

A good reducing agent. Contains carbon which reduces lead from Litharge.

Fire Assay

A branch of quantitative chemical analysis where metals are determined in ores and metallurgical products by extracting and weighing in metallic state.

Metals Determined by Fire Assay

Gold, silver, and platinum.

Gangue

The non-valuable minerals in ore.

Ores

Mineral aggregates from which one or more metals can be extracted at a profit.

Metallurgical Products

A large range of metal-bearing mixtures and compounds.

Concentrate

Grade (amount) of precise metal as compared to the waste material in a given quantity of ore or metallurgical product.

Flux

A chemical reagent which, when heated, combines with or takes into solution a difficultly fusible compound.

Slag

The liquid part resulting from fusion which contains the waste, gangue.

Dore

Product of cupellation that contains gold and silver (alloy of gold and silver).

Bullion

Gold and silver in lump or valued by weight.

Fine

Purity of gold measured per 1000 parts of gold bar.

Carat

Measure of fines (purity) of gold. Pure gold is described as 24 carat gold.

Preparation of ore sample

To be well mixed and pulverized.

Homogeneity for fire assay process

Achieved through crushing, pulverization to require size, thorough mixing and obtaining a representative sample.

Ultimate function of Slag Fusion

To separate the gold and silver alloy from the waste material.

Two liquids produced in fusion stage

Liquid lead containing the valuable minerals and liquid slag containing waste matter (gangue).

The effectiveness of fire assay to separate Au, Ag and base metals from ore depends on two properties.

Its weak affinity for non-metallic elements and its great affinity for molten lead.

The role of Lead in fire assay

Necessary for the collection of the precious metal.

Litharge (lead oxide, PbO)

Melts at 883 °C when it becomes a molten basic flux, it acts as an oxidizer and desulphurizer

Sodium carbonate (Na2CO3)

Melts at 825°C and combines with silica and alumina producing fusible silicates and aluminates.

Borax (Na2B4O7)

Melts at 742°C and it combines with or dissolves the basic and some of the acid constituents of the gauge,producing easily fusible complex borates and mixtures of borates.

Silica (SiO2)

Melts at 1755°C, combines with metallic oxides which in many cases is considered more fusible than itself.

Nitre-(KNO3)

Melts at 339° and it neutralizes the effects of an excess of reducing substances in material to be analysed.

Common salt (NaCI)

A neutral substance that melts at 819°C and sometimes used as a cover in fusion to exclude air.

Excess Acid Ore

High silica or alumina.

Excess Base Ore

High in sulfides or oxide.

Self Fluxing

Approximately equal amount of acidic and basic constituents.

Neutral Ores

Ores that have no power to reduce litharge (PbO) to metallic lead.

Oxidizing ores

Ores containing minerals that will oxidize lead back to litharge.

Reducing Ores

Those ore that contain reducing materials that will reduce lead oxide to metallic lead.

Cupellation

Process by which gold and silver are separated from lead from which they are alloyed.

Parting

Process of separating gold and silver from their alloy and is effected by means of nitric acid (HNO3).

Annealing

Heating the gold from parting process at about 650"C for about 10 minutes.

Most alloys on solidifying

Segregate to some extent, so that the cooled metal is never uniform in composition.

Flour

A good reducing agent. Contains carbon which reduces lead from Litharge.

Perfect Cupellation

The process of completely removing all traces of lead from the dore bead.

Reduction of Lead Oxide by Carbon

PbO + 2C \rightarrow 2Pb + CO_2

Fusion Stage

The stage where the ore is mixed with fluxes and melted at high temperatures.

Silver Oxidation and Reversion

2Ag(s) + O2(g) \rightarrow 2AgO(s) 2AgO(s) \rightarrow 2Ag(s) + O2(g)

Oxidation of Lead Sulfide

2PbS + 3O2 \rightarrow 2PbO + 2SO2

The ratio of the mass of the precious metal to the mass of the ore sample

Fire Assay

A branch of quantitative chemical analysis where metals are determined in ores and metallurgical products by extracting and weighing in metallic state.

Metals Determined by Fire Assay

Gold, silver, and platinum.

Gangue

The non-valuable minerals in ore.

Ores

Mineral aggregates from which one or more metals can be extracted at a profit.

Metallurgical Products

A large range of metal-bearing mixtures and compounds.

Concentrate

Grade (amount) of precise metal as compared to the waste material in a given quantity of ore or metallurgical product.

Flux

A chemical reagent which, when heated, combines with or takes into solution a difficultly fusible compound.

Slag

The liquid part resulting from fusion which contains the waste, gangue.

Dore

Product of cupellation that contains gold and silver (alloy of gold and silver).

Bullion

Gold and silver in lump or valued by weight.

Fine

Purity of gold measured per 1000 parts of gold bar.

Carat

Measure of fines (purity) of gold. Pure gold is described as 24 carat gold.

Preparation of ore sample

To be well mixed and pulverized.

Homogeneity for fire assay process

Achieved through crushing, pulverization to require size, thorough mixing and obtaining a representative sample.

Ultimate function of Slag Fusion

To separate the gold and silver alloy from the waste material.

Two liquids produced in fusion stage

Liquid lead containing the valuable minerals and liquid slag containing waste matter (gangue).

The effectiveness of fire assay to separate Au, Ag and base metals from ore depends on two properties.

Its weak affinity for non-metallic elements and its great affinity for molten lead.

The role of Lead in fire assay

Necessary for the collection of the precious metal.

Litharge (lead oxide, PbO)

Melts at 883 °C when it becomes a molten basic flux, it acts as an oxidizer and desulphurizer

Sodium carbonate (Na2CO3)

Melts at 825°C and combines with silica and alumina producing fusible silicates and aluminates.

Borax (Na2B4O7)

Melts at 742°C and it combines with or dissolves the basic and some of the acid constituents of the gauge,producing easily fusible complex borates and mixtures of borates.

Silica (SiO2)

Melts at 1755°C, combines with metallic oxides which in many cases is considered more fusible than itself.

Nitre-(KNO3)

Melts at 339° and it neutralizes the effects of an excess of reducing substances in material to be analysed.

Common salt (NaCI)

A neutral substance that melts at 819°C and sometimes used as a cover in fusion to exclude air.