Laumontite, named after its discoverer, Dr Laumont, is a form of anaclime (or analcite) with a powdery white surface. It is characterised by the fact that it is monoclinic. It has the formulae Ca(Al2Si4)O12u4H2O and a relative hardness of 4. Exposed to the air, it loses water, becomes opaque, and crumbles.
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