A wide variety of sulphur and carbon minerals and compounds are often found associated with ore deposits. These minerals can impact ore processing and how waste can be stored during mining. Identifying what minerals these elements are present in has important implications for ore and waste characterisation.
The dominant minerals that host sulphur are sulphides and sulphates. Distinguishing the proportion of each mineral type is often an important part of environmental and metallurgical characterisation of ore and waste rock. Sulphates do not produce acid during breakdown at surface conditions whereas sulphides are acid forming under the same conditions. Sulphides associated with ore can also impact the hydrometallurgical processing, such as where cyanide is used to leach gold and sulphide minerals compete to use reagents.
A range of methods are offered to determine total sulphur, sulphur hosted in sulphide minerals and sulphur hosted in sulphate minerals.
|S-IR08||S (Total)||0.01%-50%||Total sulphur by induction furnace/IR|
|S-GRA07||S (Elemental)||0.01%-100%||Solvent leach with remaining elemental sulphur analysed by gravimetric finish.|
|S-GRA06a||S (Sulphate)||0.01%-50%||HCl (15%) leach of soluble sulphates, precipitation as barium sulphate and gravimetric finish.
Note: little to no dissolution of barite/celestite.
|S-IR06a||S (Sulphide)||0.01%-50%||HCl (25%) leach to remove sulphates; induction furnace/IR. Note: little to no dissolution
|S-GRA06a||S (Sulphate)||0.01%-40%||NaCO3 leach of sulphates, precipitation as barium sulphate and gravimetric finish.|
|S-IR07||S (Sulphide)||0.01%-50%||NaCO3 leach of sulphates, induction furnace/IR.|
Identification of the minerals hosting carbon can be important for characterising the way rock will behave during processing or storage. Graphite and organic carbon can cause problems during cyanide based hydrometallurgical processing. Gold that is taken into solution during a cyanide digestion can adsorbed onto graphite and organic carbon in a process called preg-robbing.
ALS provides a wide range of methods to determine the total carbon, organic carbon, carbon in carbonate minerals, carbon in graphite, and carbon in non-carbonates.
|C-IR07||C (Total)||0.01%-50%||Total carbon by induction furnace/IR.|
|C-IR06a||C (Non-Carbonate)||0.01%-50%||HCl (25%) leach at high temperature for 1 hour to expel carbonates as CO2,
residue analysed for C by induction furnace/IR.
|C-GAS05||CO2 (Carbonate)||0.2%-50%||HClO4 digestion and CO2 coulometer.|
|C-IR18||C (Graphite)||0.02%-50%||HCl (50%) leach of carbonates, roasting to remove organic carbon, induction furnace/IR.|
|C-IR17||C (Non-Carbonate)||0.02%-100%||Slow and repeated addition of HCl (50%) to decompose and evolve carbonates as CO2.
Residual carbon is then analysed by induction furnace/IR.
|C-CAL15||C (Carbonate)||0.02%-100%||Carbonate carbon calculated by difference. Requires C-IR07, C-IR17.|
ALS offers a variety of economical packages to report both sulphur and carbon concentrations for the same sample.
Several options for combined sulphur and carbon analysis are available. Two of these are listed in the methods table but please contact ALS for other method combination packages.
|ME-IR08||C (Total) and S (Total)||0.01%-50%||Total carbon and sulphur by induction furnace/IR.|
|ME-IR06a||C (Organic) and S (Sulphide)*||0.01%-50%||Non-Carbonate carbon and sulphide sulphur by HCI (25%) leach to remove carbonates
and sulphates, induction furnace/IR.
Samples can be submitted at any ALS geochemistry location and either analysed at that location or sent to a lab that performs the method. Please contact ALS to find out the logistics for submitting your samples.
If preg-robbing is suspected during gold analysis, specialised methods can determine the propensity for a sample to preg-rob in a cyanide leach.MORE INFORMATION
Carbon and oxygen isotopes of carbonate minerals can provide a vectoring tool for carbonated host mineralisations where visible alteration is limited.MORE INFORMATION