Description
The mineral group epidote consists of a number of sorosilicates, the most important of which is the mineral epidote. The mineral epidote is a calcium-iron-aluminum-silicate with the chemical formula Ca2(Fe3+,Al)Al2(SiO4)(Si2O7)O(OH).
The yellow to brownish-green, grey, or black epidote has a vitreous luster, a greyish-white streak colour, and the cleavage is perfect according to crystal level [001]. The crystal system is monoclinic. The average density is 3.45 and the hardness is 7. Epidote is not radioactive. The name epidote is derived from the Greek epidosis, which means “addition”. Epidote is a very common mineral worldwide, particularly in contact metamorphic rocks. It is formed in crystalline limestone and in schists. Beautiful epidote crystals are found particularly in the Knappenwand, near the Großvenediger in the Untersulzbachthal, Salzburg (Austria). Epidote is common in the sand fraction of Dutch Quaternary river sediments. In heavy mineral analysis, as performed in the Netherlands by the Geological Survey during the second half of the twentieth century, the mineral is classified in the so-called unstable group.
