Marialite
Marialite is a silicate mineral with a chemical formula of Na4Al3Si9O24Cl if a pure endmember or Na4(AlSi3O8)3(Cl2,CO3,SO4) with increasing meionite content. Marialite is a member of the scapolite group and a solid solution exists between marialite and meionite, the calcium endmember. It is a rare mineral usually used as a collector's stone.
| Marialite | |
|---|---|
| General | |
| Category | Tectosilicate |
| Formula (repeating unit) | Na4Al3Si9O24Cl |
| IMA symbol | Mar |
| Strunz classification | 9.FB.15 |
| Crystal system | Tetragonal |
| Crystal class | Dipyramidal (4/m) (same H-M symbol) |
| Space group | I4/m |
| Unit cell | a = 12.06 Å, c = 7.572(3) Å; Z = 2 |
| Identification | |
| Color | Colorless, white, grey; pink, violet, blue, yellow, brown, orange-brown, pale green or reddish |
| Crystal habit | Typically flat, pyramidal striated crystals; massive, granular |
| Cleavage | Distinct on {100} and {110} |
| Fracture | Uneven to conchoidal |
| Tenacity | Brittle |
| Mohs scale hardness | 5+1⁄2–6 |
| Luster | Vitreous, pearly, resinous |
| Streak | White |
| Diaphaneity | Transparent to opaque |
| Specific gravity | 2.55–2.74 |
| Density | 2.5–2.62 g/cm3 |
| Optical properties | Uniaxial (−) |
| Refractive index | nω = 1.539–1.550 nε = 1.532–1.541 |
| Birefringence | δ = 0.007 – 0.009 |
| References | |
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