valentinite

{{infobox mineral | name = Valentinite | image = Valentinite-205948.jpg | alt = | caption = A sample of valentinite from Algeria (size: 6.9 x 4.4 x 3.3 cm) | category = Oxide minerals | formula = Sb2O3 | IMAsymbol = Vln | molweight = | strunz = 4.CB.55 | dana = | system = Orthorhombic | class = Dipyramidal (mmm) H-M symbol: (2/m 2/m 2/m) | symmetry = Pccn | unit cell = a = 4.91 Å, b = 12.46 Å c = 5.42 Å; Z = 4 | color = Colorless, snow-white, pale yellow, pink, gray to brownish | colour = | habit = Prismatic crystals, sometimes flattened, fan-shaped or stellate aggregates of crystals; lamellar, columnar, granular, massive. | twinning = | cleavage = {110}, perfect; {010}, imperfect | fracture = | tenacity = Brittle | mohs = 2.5–3 | luster = Adamantine, pearly on cleavages | streak = White | diaphaneity = Transparent to translucent | gravity = 5.76 | density = | polish = | opticalprop = Biaxial (−) | refractive = nα = 2.180 nβ = 2.350 nγ = 2.350 | birefringence = δ = 0.170 | pleochroism = | 2V = Very small | dispersion = | extinction = | length fast/slow = | fluorescence = | absorption = | melt = | fusibility = | diagnostic = | solubility = | impurities = | alteration = | other = | references = }} Valentinite is an antimony oxide mineral with formula Sb2O3. Valentinite crystallizes in the orthorhombic system and typically forms as radiating clusters of euhedral crystals or as fibrous masses. It is colorless to white with occasional shades or tints of yellow and red. It has a Mohs hardness of 2.5 to 3 and a specific gravity of 5.76. Valentinite occurs as a weathering product of stibnite and other antimony minerals. It is dimorphous with the isometric antimony oxide senarmontite.

==Historical data== Valentinite is a mineral named in the middle of the 19th century in honour of Basilius Valentinus, a writer on alchemy. He is the supposed author of the first book to give a detailed description of antimony and its compounds. From the contents of the book it is also obvious that Valentinus was familiar with the synthetic preparation of antimony trioxide, which was called 'the antimony flower'.