05-13. Tourmaline – dravite #7.

A tourmaline-dravite from Austria.

From the schorl-dravite series resource by Bosi and Lucchesi. Locality: Zillerthal, Tyrol, Austria.

05-13

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05-12

05-12. Tourmaline – dravite #6.

All I did was change the unit cell parameters specs – and out of nowhere came this unexpected star, right in the center of the polyhedra. Fun!

05-12

05-11. Tourmaline – dravite #5.

From a resource by Hughes, Rakovan, Ertl, Rossman, Baksheev and Bernhardt.

Triclinic Ni-bearing dravite from Berezovskoe, Middle Urals, Russia.

05-11

05-10

05-10. Tourmaline – dravite #4.

From a resource by  Ertl, Marschall, Geister, Henry, Schertt, Ntaflos, Luvizotto, Nasdala and Tillmanns. Metamorphic ultrahigh-pressure tourmaline from Parigi, Dora Maira, Western Alps, Italy.

05-10

05-08

05-08. Tourmaline – dravite #2.

Dravite polyhedra and atom unit cell on a tourmaline background.

From a resource by Foit & Rosenberg – vanadium-bearing tourmaline.

05-08

05-07

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.

05-07