laumontite
noun
lau·mont·ite
variants or less commonly laumonite or lomonite
lōˈmän(t‧)ˌīt
plural -s
: a white monoclinic mineral CaAl2Si4O12.4H2O consisting of a hydrous calcium and aluminum silicate and having a vitreous luster that upon exposure to the air loses water, becomes opaque, and crumbles
Word History
Etymology
laumontite, laumonite alteration of lomonite, irregular from F. P. N. G. de Laumont †1834 French mineralogist + English -ite