rapidcreekite

{{Infobox mineral | name = Rapidcreekite | category = Sulfate mineralsCarbonate minerals | boxwidth = | boxbgcolor = | image = Rapidcreekite - Rapid Creek, Yukon.jpg | imagesize = 260px | caption = Rapidcreekite from the Rapid Creek area, Yukon, Canada | formula = Ca2(SO4)(CO3)·4H2O | IMAsymbol = Rck | molweight = | strunz = 7.DG.20 | dana = 32.2.1.1 | system = Orthorhombic | class = Dipyramidal (mmm) H-M symbol: (2/m 2/m 2/m) | symmetry = Pcnb | unit cell = a = 15.517(2) Å b = 19.226(3) Å c = 6.1646(8) Å; Z = 8 | color = White to colorless | habit = Elongated, flattened to acicular crystals in radiating sprays or crust forming | twinning = | cleavage = Perfect on {010}Good on {100} | fracture = Splintery | tenacity = Brittle | mohs = 2 | luster = Vitreous | polish = | refractive = nα = 1.516nβ = 1.518nγ = 1.531 | opticalprop = Biaxial (+) | birefringence = δ = 0.015 | 2V = 45° (measured) | dispersion = None | pleochroism = | fluorescence= Non-fluorescent | absorption = | streak = White | gravity = 2.239 (calculated) | density = | melt = | fusibility = | diagnostic = | solubility = Dissolves slowly in 10% HCl | diaphaneity = Transparent | other = | references = }} Rapidcreekite is a rare mineral with formula Ca2(SO4)(CO3)·4H2O. The mineral is white to colorless and occurs as groupings of acicular (needle-shaped) crystals. It was discovered in 1983 in northern Yukon, Canada, and described in 1986. Rapidcreekite is structurally and compositionally similar to gypsum.

==Description== thumb|left|White crystals of rapidcreekite with quartz from the Rapid Creek area Rapidcreekite is transparent and white to colorless. The mineral occurs as isolated clusters or pervasive crusts of radiating sprays of acicular crystals up to in length.