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Formula: Mg(CO3).5H2O
Hydrated normal carbonate
Specific gravity: 1.6
Hardness: 2½
Streak: White
Colour: Colourless (fresh), white (exposed); colourless in transmitted light
Solubility: Effloresces readily, altering to nesquehonite. Soluble in
dilute acids with effervescence.
Environments
Lansfordite remains stable for several months at room temperature, but may slowly dehydrate, ultimately altering
to nesquehonite. Associated minerals include
nesquehonite,
hydromagnesite and dypingite
(HOM, Mindat).
Localities
At Atlin, Atlin Mining Division, British Columbia, Canada, lansfordite occurs in a
hydromagnesite deposit, the cavities of which are lined with thin films
of translucent lansfordite. These films do not exceed one millimeter in thickness and, as a rule, are thinner
(AM 9.225-228).
At the Lake Huleh Preserve, Northern Jordan Valley, Northern District, Israel, lansfordite occurs in desert
plants.
The saguaro is a cactus that grows to 15 m tall and weighs up to several tons, of which 85% to 90% of the mass
is water. Roughly 18% of the dry mass consists of the biomineral weddellite,
derived from atmospheric carbon dioxide by photosynthesis. After the death of the saguaro, minerals crystallise in the
rotting flesh, formed from elements released from the decay of the cactus by microorganisms.
During the initial stages of decay, minerals formed include lansfordite,
nesquehonite, glushinskite,
monohydrocalcite, calcite and
vaterite. Further decay produces warm, moist pockets within the dead saguaro
that contain abundant, glassy lansfordite crystals to 1 mm in diameter. Then
nesquehonite and
monohydrocalcite crystallise and finally a pale-brown to tan-coloured
sand of weddellite and its transformation product
monohydrocalcite. This
monohydrocalcite further alters to
calcite. Decay of the saguaro adds atmospheric carbon to the soil as inorganic
carbon from the transformation of the biomineral weddellite to
calcite
(AM 88.1879-1888).
At Feragen, Røros, Trøndelag, Norway, lansfordite occurs as a weathering product of an
ultramafic body
(HOM).
At the type locality, the Nesquehoning Coal mine, Nesquehoning, Lansford, Carbon county, Pennsylvania, USA,
lansfordite occurs as small stalactites attached to carbonaceous shale in the underground workings of an
anthracite coal mine underground workings. The only associated mineral that has been reported is
nesquehonite
(Mindat, HOM).
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