Serpentine
Serpentine is not the name of a distinct mineral species but is the name of a group of minerals: the Serpentine Group. The Serpentine Group includes Antigorite, Chrysotile and Lizardite. These three minerals are polymorphous, meaning they have essentially the same chemistry but different structures. Antigorite is a fairly common member of the group, but Lizardite is the most abundant Serpentine. The Serpentine Group is a subgroup of the Kaolinite-Serpentine Group. The Serpentine Group describes a group of common rock-forming magnesium phyllosilicate minerals that may contain minor amounts of other elements including chromium, cobalt, iron, manganese or nickel. As the members of the Serpentine Group are not always easy to differentiate from one another, they may just be referred to as Serpentine.
Serpentine was named in 1564 by Georgius Agrigola (1494-1555) from the Latin word serpens meaning snake in allusion to the mottled green appearance of the mineral suggesting the resemblance to some snakes. Georgius Agrigola was a German Catholic scholar and scientist known as “the father of mineralogy”. His birth name was Georg Pawer (Bauer in modern German). Agricola is the Latinized version of his name, by which he was known his entire adult life. Agricola and Bauer mean “farmer” in their respective languages. He is best known for his book De Re Metallica (Latin for On the Nature of Metals (Minerals)). It is a book cataloguing the state of the art of mining, refining, and smelting metals at the time. It was published in 1556, a year after his death, due to a delay in preparing woodcuts for the text. The book was the authoritative text on mining for 180 years after its publication. It was also an important chemistry text for the period and is significant in the history of chemistry.
Distribution: Probably the most common serpentine mineral. A few prominent localities for well-studied material include: at Kennack Cove, The Lizard, Cornwall, England. On Unst, Shetland Islands, Scotland. From near Val Sissone, Lombardy, and Val Trebbia, Piacenza, Italy. In Japan, from Maruo Odori and Kodo, Yamaguchi Prefecture, and at Hamao, Fukuoka Prefecture. At Woodsreef, New South Wales, Australia. From the Jeffrey mine, Asbestos, Quebec, and the Cassiar mine, British Columbia, Canada. In the USA, in the Stillwater complex, Montana.
| Chemical Formula: | D3[Si2O5](OH)4 +/- n(H2O); (Serpentine Group) Mg3(Si2O5)(OH)4; (Antigorite, Lizardite & Chrysotile) |
| Magnesium Silicate Hydroxide (Antigorite, Lizardite & Chysotile) | |
| Molecular Weight: | 277.11 gm (Lizardite) |
| Composition (Lizardite): | Magnesium | 26.31 % | Mg | 43.63 % | MgO |
| Silicon | 20.27 % | Si | 43.36 % | SiO2 | |
| Hydrogen | 1.45 % | H | 13.00 % | H2O | |
| Oxygen | 51.96 % | O | |||
| 100.00 % | 100.00 % | = TOTAL OXIDE |
| Crystallography: | Triclinic – Pinacoidal (Lizardite) |
| Crystal Habit: | (Lizardite) Crystals rare, to 2 mm, as trigonal plates to truncated trigonal pyramids. Commonly as extremely fine-grained scales and massive aggregates. |
| Twinning: | None |
| Cleavage: | Perfect on {0001} |
| Fracture: | n/a |
| Tenacity: | Crystals are easily bent. |
| Moh’s Hardness: | 2.5 |
| Density: | 2.55 (g/cm3) |
| Luminescence: | None |
| Radioactivity: | Not Radioactive |
| Color: | Green, light yellow to white; colorless to pale green in thin section |
| Transparency: | Translucent |
| Luster: | Waxy |
| Refractive Index: | 1.538 – 1.568 Uniaxial (-) to slightly Biaxial (-) |
| Birefringence: | 0.012 |
| Dispersion: | Weak to distinct |
| Pleochroism: | n/a |
