Clinohumite is a rare mineral and an especially rare gemstone. It is a member of the humite group of minerals, which include humite, clinohumite, chondrodite and norbergite.
The humite minerals are named after Sir Abraham Hume (1749-1838), an English mineralogist and famous art collector. Among the paintings that Hume once owned are Titian's "Death of Actaeon" (now in the National Gallery in London) and Rembrandt's "Aristotle Contemplating the Bust of Homer" (now in the Metropolitan Museum of Art in New York).
Clinohumite was first discovered in 1876. The first specimens were discovered in limestone blocks that had erupted from Mount Vesuvius, near Naples, Italy.
Only three sources for gem-quality clinohumite are known. They are the Pamir Mountains of Tajikistan, the Taymyr region of Northern Siberia and the Mahenge Plateau of Tanzania. Clinohumite is one of two humite group minerals that have been cut as gems, the other being the much more common chondrodite. clinohumite deposits were discovered only recently; the Pamir find in the early 1980s, the Taymyr in 2000 and the Tanzanian in 2005. Until very recently clinohumite was thought to be one of the rarest gemstones in the world with only a few thousand carats known to exist in private collections. When we had a chance to buy some clinohumite specimens recently we were skeptical of their authenticity until we had them verified at a gemological laboratory.
Clinohumite is composed of magnesium silicate and has a hardness of 6 on the Mohs scale. Gem-quality specimens have a resinous to vitreous luster. It has a specific gravity of 3.2 to 3.4, with a similar density to peridot and diopside. Its refractive index is 1.631 to 1.668, ranking between apatite and peridot. Clinohumite has poor basal cleavage.
Clinohumite colors range from light to dark-brown and from yellow to orange. The yellow-orange in particular can be quite vibrant and high quality pieces are faceted.
- First Published: July-03-2009
- Last Updated: September-25-2014
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