Massicot is lead (II)

oxide mineral The oxide mineral class includes those minerals in which the oxide anion (O2−) is bonded to one or more metal alloys. The hydroxide-bearing minerals are typically included in the oxide class. The minerals with complex anion groups such as the si ...

with an orthorhombic lattice structure. Lead(II) oxide (formula: PbO) can occur in one of two lattice formats,

orthorhombic In crystallography, the orthorhombic crystal system is one of the 7 crystal systems. Orthorhombic lattices result from stretching a cubic lattice along two of its orthogonal pairs by two different factors, resulting in a rectangular prism with a r ...

and

tetragonal In crystallography, the tetragonal crystal system is one of the 7 crystal systems. Tetragonal crystal lattices result from stretching a cubic lattice along one of its lattice vectors, so that the cube becomes a rectangular prism with a square ...

. The tetragonal form is called

litharge Litharge (from Greek lithargyros, lithos (stone) + argyros (silver) ''λιθάργυρος'') is one of the natural mineral forms of lead(II) oxide, PbO. Litharge is a secondary mineral which forms from the oxidation of galena ores. It forms as coa ...

. PbO can be changed from massicot to litharge (or vice versa) by controlled heating and cooling. At room temperature massicot forms soft (

Mohs hardness The Mohs scale of mineral hardness () is a qualitative ordinal scale, from 1 to 10, characterizing scratch resistance of various minerals through the ability of harder material to scratch softer material. The scale was introduced in 1812 by th ...

of 2) yellow to reddish-yellow, earthy, scaley masses which are very dense, with a

specific gravity Relative density, or specific gravity, is the ratio of the density (mass of a unit volume) of a substance to the density of a given reference material. Specific gravity for liquids is nearly always measured with respect to water (molecule), wa ...

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. The definition of massicot as orthorhombic PbO dates from the 1840s, but the substance massicot and the name massicot has been in use since the late medieval era. There is some evidence that the ancient Romans used the substance.''Archaeomineralogy''
by George Robert Rapp, year 2002, page 173, says three lead oxides were known to the ancient Romans:

minium ''Minium'' is a genus of thalloid alga Algae (; singular alga ) is an informal term for a large and diverse group of photosynthetic eukaryotic organisms. It is a polyphyletic grouping that includes species from multiple distinct clades. I ...

, litharge, and massicot. It may occur as an

oxidation Redox (reduction–oxidation, , ) is a type of chemical reaction in which the oxidation states of substrate change. Oxidation is the loss of electrons or an increase in the oxidation state, while reduction is the gain of electrons or a d ...

product of other lead-bearing minerals such as

galena Galena, also called lead glance, is the natural mineral form of lead(II) sulfide (PbS). It is the most important ore of lead and an important source of silver. Galena is one of the most abundant and widely distributed sulfide minerals. It cryst ...

bournonite Bournonite is a Sulfosalt minerals, sulfosalt mineral species, trithioantimoniate of lead and copper with the formula PbCuSbS3. It was first mentioned by Philip Rashleigh (1729–1811), Philip Rashleigh in 1797 as an ore of antimony and was mor ...

boulangerite Boulangerite is an uncommon monoclinic orthorhombic sulfosalt mineral, lead antimony sulfide, formula Pb5Sb4S11. It was named in 1837 in honor of French mining engineer Charles Boulanger (1810–1849),http://www.mindat.org/min-738.html Mindat a ...

, either naturally or in industrial processing. When massicot is found in a natural environment, some other minerals that may be found with it may include

cerussite Cerussite (also known as lead carbonate or white lead ore) is a mineral consisting of lead carbonate (PbCO3), and is an important ore of lead. The name is from the Latin ''cerussa'', white lead. ''Cerussa nativa'' was mentioned by Conrad Gessner ...

, litharge,

wulfenite Wulfenite is a lead molybdate mineral with the formula Pb Mo O4. It can be most often found as thin tabular crystals with a bright orange-red to yellow-orange color, sometimes brown, although the color can be highly variable. In its yellow form ...

valentinite Valentinite is an antimony oxide mineral with formula Sb2 O3. 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 ...

and

limonite Limonite () is an iron ore consisting of a mixture of hydrated iron(III) oxide-hydroxides in varying composition. The generic formula is frequently written as FeO(OH)·H2O, although this is not entirely accurate as the ratio of oxide to hydroxid ...

References

* Palache, C., H. Berman, and C. Frondel (1944) Dana’s system of mineralogy, (7th edition), v. I, 516–517 Oxide minerals Lead minerals Alchemical substances Orthorhombic minerals Minerals in space group 57 {{oxide-mineral-stub