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NaMg3Al6B3Si6O27(OH,F)4
Hexagonal
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| Figure 16-26. Prismatic dravite crystals from Franklin. Specimen is 10 cm in maximum dimension. Smithsonian Institution, #R3956. Photo by Vic Krantz. | ||
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Dravite, a sodium magnesium aluminum boron silicate hydroxide mineral of the tourmaline group, is uncommon at Franklin. One specimen has been analyzed and found to be dravite (Dunn et al. 1977). These crystals are dark green, 25 mm in length, composed of trigonal prisms and pedions, and markedly prismatic in habit (Figure 16-26), quite unlike the common equant habit of most Franklin uvite. They are associated with calcite and pyrrhotite from the Franklin Marble. An analysis of these crystals is given in Table 9, together with an analysis of a black ferrian dravite which occurs as massive material associated with quartz on the 1600 level of the Sterling Mine.
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| Copyright © 1995 by Pete J. Dunn |
Website
by Herb Yeates
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Link
to homepage
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This
page created: January 11, 2001 |
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