Serpentine

Mineral Name: Serpentine

Chemical Composition: (Mg,Fe,Ni,Al,Zn,Mn)2-3(Si,Al,Fe)2O5(OH)4 (2)

Color: Usually various shades of green or yellow, can be multicolored black, grey, white (1)

Streak: White (1)

Hardness: Has a variable hardness, 3-6. Usually softer than granite and harder than marble. (2)

Cleavage/Fracture: The cleavage is usually not discernible because of crystal development.

Chrysotile, a variety of serpentine, may exhibit basal cleavage. (3) Basal cleavage can be seen on minerals in the mica group. This type of cleavage is shown by the mineral peeling into sheets. (10)

Crystal Form: Serpentine crystal form can be massive, platy, fibrous, botryoidal (which looks like a clump of grapes), columnar, earthy, platy, micaceous, or can be found in pyramidal groupings. (3) It can pseudomorph, which means that it can replace another mineral without changing the crystal form of the original mineral. (11)

Luster: greasy, waxy (1)

Special Features: Serpentine can be elastic or flexible. (1) Serpentine can also feel greasy or soapy.

Varieties: Asbestos is very fibrous and flexible. Bowenite is usually greenish and fibrous. Deweylite is can contain other minerals like talc or stevensite. Garnierite contains nickel. Picrolite occurs in a columnar crystal habit. Verde Antique is a dark green rock used as a decorative stone and is sometimes mistaken for marble. Williamsite is a translucent green. (3)

Mineral Group: Serpentine is part of the silicate mineral group meaning that it contains various amounts of the elements silicon and oxygen. (1, 12) It also has phyllosilicates, which is a group of silicates that have each set of tetrahedrons surrounded by three oxygen atoms, forming a sheet like structure. (13)

Environment: Serpentine is common in many environments but is mainly found where metamorphic rocks exist since serpentine is an important rock forming mineral in metamorphic environments. Metamorphic rocks can be found in places where there is magma, so serpentine can be found in intrusive rock forming environments.(4) Serpentine is metamorphosed ultramafic rock, so it is abundant at convergent plate boundaries, like subduction zones. (2) Here, the oceanic plate is forced into the mantle where there extreme pressure and also water which is necessary in the formation of serpentine. (2) Serpentine can be exposed along “sutures zones” of ophiolites, where oceanic rocks have been thrust up on land during accretion. (2)

Associated Rock types: Metamorphic rocks that essentially consist of serpentine are called serpentinite. Other metamorphic rocks that are associated with ophiolites are ophicarbonate, ophicalcite, and ophimagnesite. Another rock type is of containing serpentine is an igneous rock that consists of chromitite. (14)

Occurrence in North America: Serpentine is very common so it is in a lot places worldwide. A few of those places in the U.S. consist of California, Arizona, New Jersey, New York, Pennsylvania, and Vermont. (3) The Klamath/Siskiyou Mountains of northwest California along with southwest Oregon, have been said to have the highest amount of serpentine found in North America. (5)

Economic Uses: Bowls, vases, desk sets, clock bases, animals, fruit, flowers, and statues are all common objects carved from serpentine by artists that are sold. (2) Serpentine is soft and easy to carve, but samples without voids and fractures is preferred. (2) Serpentine can also be cut into gemstones for jewelry that can also be sold. (2)

Industrial Uses: Serpentine can be used by the construction industry as dimension stone (blocks or slabs), in cement manufacturing, and for road aggregate.(6) One extensive use of serpentine has been for insulation and fire suppression through asbestos. Some varieties of serpentine have a fibrous form that resists heat, insulate, and do not burn. The use of asbestos in construction products such as wall tiles, flooring, stoves, paints and other common building materials was very common in the 20th century. (2) The use of asbestos was eventually ended since it was later connected to lung cancer and other sorts of cancers due to the shape and size of the associated fibers. (2)

First Notable Identification: Around the areas of Pope and the West Greenland Ice fields, there are some of the oldest rocks found that are associated with early life on Earth. Also, serpentine has probably been present since human-life started but since the historic record only goes back so far, no one can confirm the exact date of identification. (8) Serpentine was first named in 1564 by Georgius Agricola from the Latin “serpens” which means snake, because of its green color that looks like some snakes. (14)

How We Identified It: Serpentine can be identified by its dark mottled green color and snake like pattern or stripes. The texture feels very soapy and slippery and it can be recognized by its hardness of 3-6 if scratched against a piece of glass.

Don’t Confuse It With: Serpentine is often confused with Translucent Black Omphacite Jadeite Jade and olivine. (4) Olivine is usually only one shade of green, often lighter in color too, where as serpentine is usually darker shades of green and light green with black, along with stripe like patterns. Olivine is also harder. Translucent Black Omphacite Jadeite Jade is harder, and darker green with more black color and has more of a glassy looking texture. People confuse these two minerals mainly because their colors are relatable.