Lansfordite: Properties and Occurrences

Lansfordite is a hydrated magnesium carbonate mineral with composition: MgCO3·5H2O. It is a soft monoclinic hydrated magnesium carbonate mineral. It is a mineral composed of a hydrous basic carbonate of magnesium like paraffin when first taken out of the ground but altering to nesquehonite on exposure.

Landsfordite was discovered in 1888 in a coal mine in Lansford, Pennsylvania.

General information:

  • Formula: MgCO3 5H2O
  • Color: Colorless (fresh), white (exposed); colorless in transmitted light.
  • Hardness: 2½
  • Specific Gravity: 1.6
  • Crystal System: Monoclinic.

Fig: Lansfordite

Physical Properties

It crystallizes in the monoclinic system and typically occurs as colorless to white prismatic crystals and stalactitic masses. It is a soft mineral, Mohs hardness of 2.5, with a low specific gravity of 1.7. It is transparent to translucent with refractive indices of 1.46 to 1.52.

  • Cleavage: {001} Perfect, {100} Distinct
  • Density: 1.7
  • Diaphaneity: Transparent to Opaque
  • Hardness: 2.5 – Finger Nail
  • Luminescence: Non-fluorescent.
  • Luster: Vitreous – Dull
  • Magnetism: Nonmagnetic
  • Streak: white

Occurrence: Stalactites pendant from the shale roof of an anthracite coal mine (Nesquehoning, Pennsylvania, USA); in a hydromagnesite deposit (Atlin, Canada); a weathering product of an ultramafic body (Sør-Trøndelag, Norway).

Association: Nesquehonite, hydromagnesite, dypingite.