marshite

{{Infobox mineral | name = Marshite | boxwidth = | boxbgcolor = | image = Marshite.jpg | imagesize = | alt = | caption = Exceptionally well crystallized specimen of the rare copper iodide marshite from the Rubtsovskoe Deposit, Altaiskii Krai, Western Siberia, Russian Federation. | category = Halide mineral | formula = CuI | IMAsymbol = Msh | strunz = 3.AA.05 | dana = 9.1.7.3 | system = Isometric | class = Hextetrahedral (3m) | symmetry = F3m | unit cell = a = 6.05 Å (untwinned a = 6.6063(1) Å); Z=4 | color = Honey-yellow, exposed to air pink-red to brick-red | habit = Tetrahedral crystals, cubo-octahedral, crusts | twinning = On {111} | cleavage = {011} perfect | fracture = Conchoidal | tenacity = Brittle | mohs = 2.5 | luster = Adamantine, greasy | streak = Yellow | diaphaneity = Transparent | gravity = 5.68 | density = 5.68 g/cm3 (measured), 5.71 g/cm3 (calculated) | polish = | opticalprop = Isotropic | refractive = | birefringence = | pleochroism = | 2V = | dispersion = | extinction = | length fast/slow = | fluorescence = Dark red (SW, LW) | absorption = | melt = | fusibility = | diagnostic = | solubility = | impurities = | alteration = | other = | references = }}

Marshite (CuI) is a naturally occurring isometric halide mineral with occasional silver (Ag) substitution for copper (Cu). Solid solution between the silver end-member miersite and the copper end-member marshite has been found in these minerals from deposits in Broken Hill, Australia. The mineral's name is derived from the person who first described it, an Australian mineral collector named Charles W. Marsh. Marsh drew attention to native copper iodide (Marshite) in the 1800s emphasizing its natural occurrence, it is not to be confused with copper (I) iodide a substance commonly synthesized in laboratory settings.