FOV 2.4 x 3.2 mm. Modris Baum coll. This is an XRD analyzed specimen from the Poudrette pegmatite (Thanks to Dr. AMcD. We were both very surprised by the result.) The red/brown resinous "caps" usually seen on earlier finds are totally absent here. (According to the 2001 paper describing natrolemoyinite [1] , these caps are lepidocrocite, not hisingerite, as has often been alleged.) Nov 2017: Recent qualitative EDS indicates that this is actually end-member natrolemoynite - there is no Ca in the spectrum. — Photo: Modris Baum · CC0
Natrolemoynite
Natrolemoynite is an IMA-recognized mineral species in the silicate class, with the chemical formula Na₄Zr₂Si₁₀O₂₆·9H₂O.
It crystallizes in the monoclinic crystal system (space group C2/m). It is a member of the Lemoynite structural group.
Key properties: Mohs hardness 3; specific gravity 2.47; White streak; Vitreous to subadamantine luster; optically biaxial.
IMA symbol Nlm, IMA status: approved, named in 1996.
Late stage in pegmatite cutting nepheline syenite.
It is found associated with Microcline, lemoynite, lepidocrocite, galena, sphalerite, calcite, pyrite (in altered pegmatite); biotite, microcline, albite, magnetite, chlorite.
Alludes to the Na dominance (natro) and polymorphic relationship to lemoynite. Type: Canadian Museum of Nature, Ottawa, Ontario, Canada (81534).