149 - Gypsum

ID	149
Mineral	Gypsum
Location	Lubin - Woiwodschap Neder-Silezië - Poland
Fluorescence	LW-UV: close SW-UV: close
Mindat.org	View Gypsum information at mindat.org

ID	1784
Long ID	1:1:1784:4
Formula	`Ca(SO₄) · 2H₂O`
IMA Status	0 1
Other Occurrences	Commonest of the sulphate minerals, gypsum is found in marine evaporites, in caves where the air is dry enough to allow it to be deposited and remain, at fumaroles, and in the oxidized zones of sulfide deposits on occasion.
Industrial	Plaster, plasterboard.
Diapheny	Transparent,Translucent,Opaque
Cleavage	Perfect (eminent) and easy on {010}, almost micaceous in some samples; on {100} distinct, yielding a surface with a conchoidal fracture; on {011}, yielding a fibrous fracture {001}.
Tenacity	flexible
Colour	Colourless to white, often tinged other hues due to impurities; colourless in transmitted light.
Hardness (min)	2.0
Hardness (max)	2.0
About the name	First known mention is by Theophrastus about 300-325 BCE from the Greek γυψοζ (gypsos) meaning plaster.
Streak	White.
Crystal System	Monoclinic
Cleavage Type	Perfect
Fracture type	Splintery,Conchoidal
Morphology	Thin to thick tabular crystals, {010} with {_111} and {120}; also prismatic [001], stout to acicular, with the prism zone often striated. Crystals may have warped surfaces or may be bent or twisted. Rosette-like clusters of lenticular crystals are common. Also found as granular masses, massive beds, and fibrous masses ("satin spar").
Twinning	{100} ("swallow-tail"), very common, with a re-entrant angle formed ordinarily by {_111}; on {_101} as contact twins ("butterfly" or "heart-shaped"), along {_111}; on {_209}; also as cruciform penetration twins.
UV	Common and varied. Most common colours of fluorescence are baby-blue and shades of golden yellow to yellow. Selenite crystals often exhibit zoned "hourglass" fluorescence in zones that may, or may not, be evident in ordinary light.
Thermal Behaviour	Dehydrates and turns white. Heated in a closed tube, it gives off water and becomes opaque. Fuses at 2.5-3, coloring the flame reddish yellow.
Comment Luster	Wide range of luster based on varieties, pearly on {010}
shortcode_ima	Gp
Group	Gypsum Supergroup

Symbol	Element
Ca	Calcium
H	Hydrogen
O	Oxygen
S	Sulfur

Gypsum

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