massicot

{{Infobox mineral | name = Massicot | boxwidth = | boxbgcolor = | image = File:Massicot-177335.jpg | imagesize = 260px | alt = | caption = Massicot from the Monte Cristo mine, Goodsprings District, Clark County, Nevada (size: 5.0 x 4.0 x 4.0 cm) | category = Oxide mineral | formula = PbO | IMAsymbol = Msi | molweight = | strunz = 4.AC.25 | dana = | system = Orthorhombic | class = Dipyramidal (mmm) H-M symbol: (2/m 2/m 2/m) | symmetry = Pbcm | unit cell = a = 5.4903 Å, b = 5.892 Å, c = 4.752 Å; Z = 4 | color = Yellow may have a red tint | colour = | habit = Scaly as incrustations, massive | twinning = | cleavage = Distinct on {100} and {010} | fracture = Flexible | tenacity = | mohs = 2 | luster = Greasy to dull | streak = Yellow | diaphaneity = Translucent | gravity = 9.642 calculated | density = | polish = | opticalprop = Biaxial (+) | refractive = nα = 2.510 nβ = 2.610 nγ = 2.710 | birefringence = δ = 0.200 | pleochroism = Y = light sulfur-yellow; Z = deep yellow | 2V = Measured: 90°, calculated: 86° | dispersion = Strong | extinction = | length fast/slow = | fluorescence = | absorption = | melt = | fusibility = | diagnostic = | solubility = | impurities = | alteration = | other = | prop1 = | prop1text = | references = }}

Massicot is a lead (II) oxide mineral with an orthorhombic lattice structure. Lead(II) oxide (formula: PbO) can occur in one of two lattice formats, orthorhombic and tetragonal. The red tetragonal form is called litharge. PbO can be changed from massicot to litharge (or vice versa) by controlled heating and cooling. At room temperature massicot forms soft (Mohs hardness of 2) yellow to reddish-yellow, earthy, scaley masses which are very dense, with a specific gravity of 9.64. Massicot can be found as a natural mineral, though it is only found in minor quantities. In bygone centuries it was mined. Nowadays massicot arises during industrial processing of lead and lead oxides, especially in the glass industry, which is the biggest user of PbO.