On November 24 I reported on the Denver Area Mineral
Dealers fall 2019 Gem and Mineral Show held at the Jefferson County Fairgrounds
on November 15-17. I picked up some
nifty minerals (see the Post) but thought I ought to mention the Best $2
Mineral Added To My Collection! In
fact, I thought it was a real find—a gemmy green cluster of dioptase crystals,
a hydrated copper silicate [CuSiO3-H2O].
A cluster of gemmy green dioptase crystals. Width of specimen ~3 cm.
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Dioptase crystals. Width FOV ~1.8 cm.
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Drawing of dioptase, modified rhombohedral crystal. Courtesy of smorf.nl with original from Goldschmidt, Atlas de Krystallformen, 1913-1923.
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Nice modified rhombohedral crystals of dioptase (Trigonal Crystal System). Width FOV ~ 4 mm.
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Drawing of dioptase, modified rhombohedral crystal. Courtesy of smorf.nl with original from Goldschmidt, Atlas de Krystallformen, 1913-1923.
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The “softness” of dioptase (5.0 Mohs) easily
distinguishes them from hard emeralds (8.0 Mohs)—for those of you who identify
minerals for treasure hunters. In fact,
in the late 1700s copper miners working at the Altyn-Tyube Mine in the Ural
Mountains of Kazakhstan thought they had discovered a giant emerald deposit
when suddenly beautiful green crystals started showing up. I presume many of the green crystals were
taken out via lunch bucket by the Russian and Kazakh miners before the
mineralogists/chemists working in Moscow said, “sorry boys, too soft for
emeralds.” Even today the Altyn-Tyube in
the premier collecting locality for dioptase and the source of my specimen.
Dioptase forms in the oxidized zone as a secondary
mineral where copper sulfides are the primary minerals. However, the formation
of diopside is restricted to dry climates where circulating ground water has an
alkaline pH (acidic solutions buffered by carbonates) and dissolved copper. Dioptase is closely related to another copper
silicate, chrysocolla.
And finally, dioptase may be, and has been, used as a
pigment for painting.
The though for Monday: Green is the prime color of the world, and that from which its loveliness arises. Pedro Calderon de la Barca.
The though for Monday: Green is the prime color of the world, and that from which its loveliness arises. Pedro Calderon de la Barca.
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