Ultramafic Rocks – Serpentinites, Soapstone and Talc-stone

Serpentinite, soapstone and talc-stone are technical and commercial designations used for the metamorphic variety of ultramafic rocks. Serpentine, tremolite/actinolite, chlorite, talc and carbonates, in several associations basically determine the mineralogical constitution of those varieties. In the sector of dimension and covering stones, serpentinites are commonly treated like marbles (for instance: Green Alpi and Green Guatemala).

Serpentinites have dark-green color, show stronger resistance to abrasion and accept polishing, being used for coverings in masonry. The greatest problem in the extraction of the sepentinites refers to the high degree of fracturing still in the rock bulks; this leads to quite low rates of recuperation and only for small dimension blocks.

Soapstone é a little softer than the serpentinites, presents a dark-gray color and is specially used for the manufacturing of domestic stoves, fireplaces, small coverings, pans, casseroles, plates, grills for cooking, as well as other decoration use. Its main characteristic is the possibility of using high temperature (till 1500 degrees C) and it keeps heat, remaining hot for long periods of time.

A fingernail can scratch the so-called talc-stone and it is unctuous when touched, speckled and presented in colours between brown and greenish. Its main use is for decoration handicraft objects, especially in statuary art. Fragments of talc-stone can be used for handiwork, in a special manner for the development of fine motor coordination of children at preschool.