plattnerite

{{Infobox mineral | name = Plattnerite | category = Oxide minerals | boxwidth = | boxbgcolor = | image = Galena-Quartz-136082.jpg | imagesize = | caption = Quartz and galena sample, plattnerite over the large galena cube. | formula = PbO2 | IMAsymbol = Ptn | molweight = 239.20 g/mol | strunz = 4.DB.05 | system = Tetragonal | class = Ditetragonal dipyramidal (4/mmm) H–M Symbol: (4/m 2/m 2/m) | symmetry = P42/mnm | unit cell = a = 4.95 Å, c = 3.38 Å; Z = 2 | color = Dark brown, iron-black | habit = Prismatic crystals, may be nodular or botryoidal, fibrous and concentrically zoned, massive | twinning = Contact and penetration twinning on {011}, rarely polysynthetic | cleavage = None | fracture = Sub-conchoidal, fibrous | tenacity = Brittle | mohs = 5.5 | luster = Bright metallic to adamantine | refractive = nω=2.35, nε=2.25 | opticalprop = Uniaxial (-) | birefringence = δ = 0.1 | pleochroism = | streak = Chestnut brown | gravity = 8.5–9.63, average = 9.06 | melt = | fusibility = | diagnostic = | solubility = | alteration = tarnishes to dull on exposure | diaphaneity = Subtranslucent to opaque | other = Non-fluorescent, nonmagnetic | references = }} Plattnerite is an oxide mineral and is the beta crystalline form of lead dioxide (β-PbO2), scrutinyite being the other, alpha form. It was first reported in 1845 and named after German mineralogist Karl Friedrich Plattner. Plattnerite forms bundles of dark needle-like crystals on various minerals; the crystals are hard and brittle and have tetragonal symmetry.

==Occurrence== Plattnerite is found in numerous arid locations in North America (US and Mexico), most of Europe, Asia (Iran and Russia), Africa (Namibia) and Southern and Western Australia. It occurs in weathered hydrothermal base-metal deposits as hay-like bundles of dark prismatic crystals with a length of a few millimeters; the bundles grow on, or sometimes within various minerals, including cerussite, smithsonite, hemimorphite, leadhillite, hydrozincite, rosasite, aurichalcite, murdochite, limonite, pyromorphite, wulfenite, calcite and quartz.