Peridotite Thin Section

Introduction to mineralogy and petrology 2014 volcanic successions associated with ore deposits.

Peridotite thin section. Peridotite is the general name for the ultrabasic or ultramafic intrusive rocks dark green to black in color dense and coarse grained texture often as layered igneous complex. Formed in the upper part of the mantle just below the earth s crust peridotite is known as a plutonic rock or alternatively ultramafic indicating that the rock contains less than 45 silica it is here seen in a thin section 24 x 32 mm under transient cross polarised light explaining the lively colours of olivine which is the primary mineral in peridotite together with other mafic minerals such. The 29 mm long dimension is actually shorter than a typical thin section which is usually between 38 mm and 42 mm.

This image shows a full thin section of horoman peridotite. In thin section the rock appears pale green a colour caused by the serpentine minerals that are formed by the breakdown of olivine. Peridotite is a non specific name used for coarse grained dark colored igneous rocks.

The thin section is dominated by large cracked plates of olivine with unusually high birefringence colours the thin section may be a little more than 30 microns thick pale green grains of pyroxene with slightly lower relief and evidence of cleavage plagioclase feldspar apparently filling pore spaces and opaque chromite grains.