Datolite from Far East of Russia (Nikolaevskiy mine

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Tourmaline -

en.wikipedia.org
Datolite is a calcium boron hydroxide nesosilicate, CaBSiO4(OH). Datolite crystallizes in the monoclinic system forming
prismatic crystals and nodular masses. The luster is vitreous and may be brown, yellow, light green or colorless. The Mohs
hardness is 5.5 and the specific gravity is 2.8 - 3.0. The type localities are in the diabases of the Connecticut River valley
and Arendal, Aust-Agder, Norway. Associated minerals include prehnite, danburite, babingtonite, epidote, native copper,
calcite, quartz and zeolites. It is common in the copper deposits of the Lake Superior region of Michigan. It occurs as a
secondary mineral in mafic igneous rocks often filling vesicles along with zeolites in basalt. Unlike most localities throughout
the world, the occurrence of datolite in the Lake Superior region is usually fine grained in texture and possesses colored
banding. Much of the coloration is due to the inclusion of copper or associated minerals in progressive stages of
hydrothermal precipitation.
Botryolite is a botryoidal form of datolite.

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PHYSICAL CHARACTERISTICS:
Color is white, colorless, yellowish, reddish, gray, brown and green.
Luster is vitreous to greasy.
Transparency: Crystals are transparent to translucent.
Crystal System: Monoclinic; 2/m
Crystal Habits include short prismatic to wedge shaped tabular crystals with complex and richly faceted terminations. Also in
porcelain-like masses that form nodules. Aggregates can be fibrous or granular.
Cleavage is absent.
Fracture is conchoidal to uneven.
Hardness is 5 - 5.5
Specific Gravity is 2.8 - 3.0
Streak is white.
Associated Minerals are prehnite, danburite, babingtonite, epidote, copper, calcite, quartz and zeolites.
Notable Occurances include Russia; Lake Superior region of Michigan and Paterson, New Jersey, USA; Bancroft, Ontario,
Canada; Charcas, Mexico; Schwarzwald, Germany and Norway.
Best Field Indicators are crystal habit, absence of cleavage, hardness and color.

www.mineralminers.com
Class: cyclosilicates
Crystal system: hexagonal-rhombohedral; 3m
Crystal habit: commonly forms prismatic crystals with well developed trigonal prism and second-order hexagonal prism
faces, can be elongated or flattened, commonly vertically striated. In cross section the prism faces often round into one
another giving the appearance of a spherical triangle. Doubly terminated crystals often show different forms at each end of
the vertical axis. Also radiating, acicular, columnar, massive.
Twinning: very rare and simple on pyramidal planes such as {1011}
Specific gravity: 2.96 - 3.31 (buergerite 3.31, dravite 3.03-3.15, elbaite 3.03-3.10, liddicoatite 3.02-3.08, schorl 3.10-3.25
and uvite 2.96-3.06)
Index of refraction: 1.610-1.735 (buergerite 1.655-1.735, dravite 1.610-1.661, elbaite 1.615-1.655, liddicoatite 1.621-1.637,
schorl 1.625-1.675 and uvite 1.612-1.638)
Birefringence: 0.016-0.080 (buergerite 0.080, dravite 0.021-0.026, elbaite 0.016-0.024, liddicoatite 0.016,schorl
0.025-0.035 and uvite 0.017-0.020)
Pleochroism: strong in all species
Hardness: 7.0 - 7.5
Color: tourmalines occur in all colors. Buergerite is dark brown to black. Dravite is usually brown to black, can be colorless.
Elbaite and liddicoatite occur in a wide range of colors and shades including green, yellow, blue, pink to red, colorless and
brown. Schorl is usually black, dark blue or dark blue-green. Uvite is usually black, brown or green. Tourmaline crystals are
often color zoned concentrically and/or along the C axis.
Luster: vitreous to resinous, can occur with chatoyancy due to tubular cavities parallel to the C axis.
Transparency: transparent to opaque
Cleavage: poor in all species except buergerite which has distinct prismatic cleavage
Fracture: conchoidal, brittle
Streak: white