Borate minerals

Borate minerals

Table
Borate minerals
name colour lustre Mohs hardness specific gravity
boracite colourless or white vitreous 7–7½ 2.9–3.0
borax colourless to white; grayish, bluish, greenish vitreous to resinous 2–2½ 1.7
colemanite colourless; white, yellowish, gray brilliant vitreous to adamantine 4½ 2.4
inyoite colourless, becoming white and cloudy after partial dehydration vitreous 2 1.7
kernite colourless vitreous 2½ 1.9
ludwigite dark green to coal black silky 5 3.6 (lud) to 4.7 (paig)
priceite white earthy 3–3½ 2.4
sussexite white to straw-yellow silky to dull or earthy 3–3½ 2.6 (szai) to 3.3 (suss)
tincalconite white (natural); colourless (artificial) vitreous 1.9
ulexite colourless; white vitreous; silky or satiny 2½ 2.0
name habit or form fracture or cleavage refractive indices crystal system
boracite isolated, embedded, cubelike crystals conchoidal to uneven fracture alpha = 1.658–1.662
beta = 1.662–1.667
gamma = 1.668–1.673 orthorhombic (isometric above 265 degrees C)
borax short prismatic crystals one perfect, one good cleavage alpha = 1.445
beta = 1.469
gamma = 1.472 monoclinic
colemanite short prismatic crystals; massive one perfect, one distinct cleavage alpha = 1.586
beta = 1.592
gamma = 1.614 monoclinic
inyoite short prisms and coarse crystal aggregates; geodes; drusy crusts; granular massive one good cleavage alpha = 1.492–1.495
beta = 1.501–1.510
gamma = 1.516–1.520 monoclinic
kernite very large crystals; fibrous, cleavable, irregular masses two perfect cleavages alpha = 1.454
beta = 1.472
gamma = 1.488 monoclinic
ludwigite fibrous masses; rosettes; sheaflike aggregates no observed cleavage alpha = 1.83–1.85
beta = 1.83–1.85
gamma = 1.97–2.02 orthorhombic
priceite soft and chalky to hard and tough nodules earthy to conchoidal alpha = 1.569–1.576
beta = 1.588–1.594
gamma = 1.590–1.597 triclinic(?)
sussexite fibrous or felted masses or veinlets; nodules alpha = 1.575–1.670
beta = 1.646–1.728
gamma = 1.650–1.732 probably orthorhombic
tincalconite found in nature as a fine-grained powder; physical properties are given for artificial pseudocubic crystals hackly fracture omega = 1.461
epsilon = 1.474 hexagonal
ulexite small nodular, rounded, or lenslike crystal aggregates; fibrous botryoidal crusts; rarely as single crystals one perfect, one good cleavage alpha = 1.491–1.496
beta = 1.504–1.506
gamma = 1.519–1.520 triclinic
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Universalium. 2010.

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