Fact Sheet:
– Chemical Composition: (Mg,Fe,Li)₅Al(Si₃Al)O₁₀(OH)₈ (variable composition with magnesium, iron, and aluminum)
– Hardness: 2 to 2.5 on the Mohs scale
– Crystal System: Monoclinic
– Color Varieties: Green, white, yellow, pink, black
– Major Localities: United States, Canada, Russia, and Italy
– Common Uses: Indicator of metamorphic conditions, industrial filler, additive in paints and plastics

Introduction: Chlorite is a group of common phyllosilicate minerals that form during the metamorphism of other minerals. Its name is derived from the Greek word “chloros,” meaning green, due to its typical color. Chlorite plays a significant role in geology as an indicator of specific metamorphic conditions and has various industrial applications.

Formation: Chlorite forms primarily through the metamorphism of mafic minerals such as biotite, amphibole, and pyroxene in low to medium-grade metamorphic environments. It can also form as an alteration product of primary igneous minerals and is commonly found in hydrothermal veins.

Types and Colors: Chlorite minerals generally exhibit a green color but can also appear in shades of white, yellow, pink, or black depending on their chemical composition and impurities. The typical green color is due to the presence of iron and magnesium.

Localities and Mining: Significant chlorite deposits are found in the United States (particularly in Vermont and New York), Canada, Russia, and Italy. While chlorite is widespread and commonly found in various geological formations, it is not typically mined for industrial use. Instead, it is often extracted incidentally during the mining of other minerals.

Applications: Chlorite has several practical applications:
– Geological Indicator: Chlorite is used as an indicator mineral in geology to determine the metamorphic conditions and history of rocks.
– Industrial Filler: Chlorite is used as a filler material in paints, plastics, and other industrial products due to its properties.
– Soil Conditioner: Chlorite can be added to soils to improve their physical properties.

Sources and further reading
http://www.minsocam.org/msa/collectors_corner/arc/chlorite.htm
https://www.mindat.org/min-968.html