Definition: Talc is defined as an hydrated magnesium sheet silicate with the chemical formula Mg3Si4O10(OH)2. Talc ore results from the metamorphism (in the presence of H2Oand CO2) of magnesium-rich country rocks. They can be roughly divided into two deposit types: TALC-CARBONATE (dominantly talc with variable amounts of chlorite, dolomite and or magnesite) and TALC-CHLORITE (dominantly talc with chlorite).

Image of talc hand specimen in rock and powder form

Analyses:  Talc samples are analysed by quantitative XRD for determination of common impurities.  These include quartz, dolomite, magnesite, calcite, chlorite, serpentine and amphibole.  Both serpentine and amphibole may occur in an asbestiform habit and we have developed a method based on an added internal standard to determine precise lower limits of detection in samples of talc for minerals such as amphibole. Talcs can also be analysed by Scanning Electron Microscopy (SEM), optical microscopy for asbestos (sub-contracted), and their colour can be measured quantitatively by spectrophotometry.