Editing Scheelite (section)

== Properties ==
[[File:CaWO4.tif|thumb|left|Structure of CaWO<sub>4</sub><ref>{{cite journal | last1 = Zalkin | first1 = A. | last2 = Templeton | first2 = D.H. | year = 1964 | title = X-ray diffraction refinement of the calcium tungstate structure | doi = 10.1063/1.1725143 | journal = Journal of Chemical Physics | volume = 40 | issue = 2| pages = 501–504 | bibcode = 1964JChPh..40..501Z | url = https://cloudfront.escholarship.org/dist/prd/content/qt7mp8m04j/qt7mp8m04j.pdf }}</ref>]]
Its crystals are in the [[tetragonal]] [[crystal system]], appearing as dipyramidal pseudo-octahedra. Colors include golden yellow, brownish green to dark brown, pinkish to reddish gray, orange and colorless. Transparency ranges from translucent to transparent and crystal faces are highly [[Lustre (mineralogy)|lustrous]] (vitreous to adamantine). Scheelite possesses distinct [[Cleavage (crystal)|cleavage]] and its fracture may be [[conchoidal fracture|subconchoidal]] to uneven. Its [[specific gravity]] is high at 5.9–6.1 and its [[Mohs scale of hardness|hardness]] is low at 4.5–5.<ref name=Handbook/> Aside from pseudo-octahedra, scheelite may be columnar, granular, tabular or massive in [[crystal habit|habit]]. [[Druse (geology)|Druzes]] are quite rare and occur almost exclusively at Zinnwald, [[Czech Republic]]. [[Crystal twinning|Twinning]] is also commonly observed and crystal faces may be striated. Scheelite [[Mineral#Streak|streak]]s white and is brittle.

Gems cut from transparent material are fragile. Scheelite's [[refractive index]] (1.918–1.937 uniaxial positive, with a maximum [[birefringence]] of 0.016) and [[dispersion (optics)|dispersion]] (0.026) are both moderately high. These factors combine to result in scheelite's high lustre and perceptible "fire", approaching that of [[diamond]].

Scheelite [[fluorescence|fluoresces]] under shortwave [[ultraviolet]] light, the mineral glows a bright sky-blue. The presence of [[molybdenum]] trace impurities occasionally results in a green glow. Fluorescence of scheelite, sometimes associated with native gold, is used by geologists in the search for gold deposits.