Lansfordite is a hydrated

magnesium Magnesium is a chemical element with the symbol Mg and atomic number 12. It is a shiny gray metal having a low density, low melting point and high chemical reactivity. Like the other alkaline earth metals (group 2 of the periodic ...

carbonate mineral with composition: MgCO₃·5H₂O. Landsfordite was discovered in 1888 in a

coal Coal is a combustible black or brownish-black sedimentary rock, formed as rock strata called coal seams. Coal is mostly carbon with variable amounts of other elements, chiefly hydrogen, sulfur, oxygen, and nitrogen. Coal is formed when ...

mine in Lansford, Pennsylvania. It crystallizes in the

monoclinic In crystallography, the monoclinic crystal system is one of the seven crystal systems. A crystal system is described by three vectors. In the monoclinic system, the crystal is described by vectors of unequal lengths, as in the orthorhombic ...

system (space group ''P2₁/c'') and typically occurs as colorless to white prismatic crystals and stalactitic masses. It is a soft mineral,

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 ...

of 2.5, with a low

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 at its dens ...

of 1.7. It is transparent to translucent with

refractive indices In optics, the refractive index (or refraction index) of an optical medium is a dimensionless number that gives the indication of the light bending ability of that medium. The refractive index determines how much the path of light is bent, or ...

of 1.46 to 1.51. The mineral will effloresce at room temperature, producing nesquehonite.

References

Magnesium minerals Carbonate minerals Geology of Pennsylvania Monoclinic minerals Minerals in space group 14 {{carbonate-mineral-stub