05-07. Tourmaline – dravite #1.
Tourmaline will be the mineral of week #19 & 20 of this – 52 grain of sand – journey.
Tourmaline is not a single mineral, but a group of 32 closely related minerals sharing the same chemical structure. The minerals are extremely varied in color. Egyptian believed that tourmaline made its journey from the center of the Earth and passed over a rainbow, taking with it all of the colors as its own. The structure of its crystal has a rounded, triangular cross-section and is part of the trigonal system. Tourmaline can range in size from less than a millimeter to over 100 pounds prisms.
Dravite and Elbaite are both tourmalines. I thought it would be interesting to study them back to back to see how much they have in common and if their geometry can bring distinct differences between them.
Dravite, this week’s tourmaline, was named after a Slovenian river by mineralogist Tschermak in the mid-1800s. Most dravite tourmalines are in the brown, to a deep brown range, some in the chromium green spectrum.
From a resource by Hamburger& Buerger: structure of a tourmaline.