Formula: NaCaB5O6(OH)6.5H2O
Origin of name: for George Ludwig Ulex (1811-1883), German chemist
Crystal system: Triclinic
Crystal class: 1
Twinning: on {010} or {100}, polysynthetic, possibly also on others
Unit cell: a = 8.81 Å, b = 12.86 Å, c = 6.68 Å, a = 90.3°, b = 109.1°, g = 105.1°
Colour: Crystals colourless, aggregates white, gray when included with clay
Diaphaneity: Transparent to opaque
Luster: Vitreous on crystals, aggregates satiny, chatoyant
Habit: Crystals acicular, greatly elongated, in nodules and lens-like masses, crusts and compact veins
Hardness: 2.5
Specific gravity: 1.95-1.96
Cleavage: 3; {010} perfect, {1-10} good, {110} poor
Tenacity: Brittle, uneven fracture across fiber groups
Streak: White
Synonyms/varieties:
Comments: Slightly soluble in water, parallel fibrous masses can act as optical fibers, may fluoresce yellow, greenish yellow, cream, white under SW- and LW-UV
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