Clinochlore is one of the more common members of the Chlorite Group of minerals. These minerals are all difficult to differentiate by ordinary means and often the general mineral name chlorite is given to specimens that lack distinguishing characteristic. Clinochlore is a secondary mineral that forms by hydrothermal alteration of other iron and magnesium silicate minerals. Clinochlore forms from the metamorphic and hydrothermal alterations of other iron and magnesium silicate minerals. Clinochlore gets its name from the Greek words for inclined and green since its structure is monoclinic and its common color is green, although the mineral can also be red, brown, tan, yellow or white.  Crystals are translucent to transparent and give a vitreous to pearly luster. Clinochlore crystals are massive, commonly foliated, fibrous and granular. Twinning is seen on some larger specimens.

Clinochlore forms a series with the mineral chamosite. Chamosite is the iron rich equivalent of clinochlore. Their properties are only slightly different with chamosite being darker and less transparent than clinochlore. A chromium rich variety of clinochlore is known as kaemmererite, which is quite beautiful and wonderfully colored bright lavender to crimson.

Clinochlore was discovered in 1851 in West Chester, Pennsylvania, USA. Some other notable localities include The Tilly Foster mine, New York, and Franklin and Sterling Hill, New Jersey, USA. Outside of the US it is found in Spain, at Kop Daglari, Turkey and in Ural Mountains, Russia.

Characteristics:

Chemistry: (Mg, Fe, Al)6(Si, Al)4O10(OH)8, Magnesium Iron Aluminum Silicate Hydroxide
Class: Silicates
Hardness (Mohs scale): 2 - 2.5
Density: 2.6 – 3.0
Crystal System: monoclinic
Crystal Habits: pseudohexagonal tabular crystals with tapering pyramidal terminations. Cleavage: perfect in one direction, basal.
Fracture: uneven.
Transparency: translucent to transparent
Luster: vitreous to pearly