Massicot Locality: Monte Cristo mine, Goodsprings District, Clark County, Nevada , USA ( Locality at mindat.org ) Size: 5.0 x 4.0 x 4.0 cm. This showy specular galena matrix specimen is VERY RICHLY covered with a mustard-yellow crust of massicot and is from the well-known Goodsprings District of Nevada. Ex. John Ydren Collection. — Photo: Robert M. Lavinsky · CC BY-SA 3.0
Massicot
The yellow tetragonal form of lead(II) oxide — litharge's polymorph, and a historic pigment.
Intro adapted from Wikipedia (CC BY-SA).
Massicot is an IMA-recognized mineral species in the oxides & hydroxide class, with the chemical formula PbO.
It crystallizes in the orthorhombic crystal system (space group Pbcm).
Key properties: Mohs hardness 2; specific gravity 9.64; Yellow streak; Greasy to dull luster; optically biaxial.
IMA symbol Msi, grandfathered status — known before the IMA’s founding, named in 1841.
Occurs as an oxidation product of galena, bournonite, boulangerite, and other lead-bearing minerals.
It is found associated with Cerussite, litharge, minium, wulfenite, antimony oxides, “limonite”.
The name comes from early Arabic, through the Spanish mazacote and the French for oxide of lead.