A recent paper in the American Mineralogist was calling for the discreditation of tetranatrolite in favour of gonnardite. This was not formally presented to the IMA, and therefore, perhaps a dubious species, tetranatrolite is still a valid species nonetheless. The paper could validate tetranatrolite as gonnardite for all but 4 locations, of which MSH is one. Another paper, soon to be published, on the crystal structure of tetranatrolite seems to validate the species. This is a photo of my first MSH specimen.
Color is white.
Luster is silky to dull. Diaphaneity is mostly opaque and rarely translucent. Crystal Habits include smalll prisms, fibrous sprays and coatings on natrolite. Hardness is 5. Streak is white.