Scapolite
The scapolites (Greek: σκάπος, "rod", and λίθος, "stone") are a group of rock-forming silicate minerals composed of aluminium, calcium, and sodium silicate with chlorine, carbonate and sulfate. The two endmembers are meionite (Ca4Al6Si6O24CO3) and marialite (Na4Al3Si9O24Cl). Silvialite (Ca,Na)4Al6Si6O24(SO4,CO3) is also a recognized member of the group.
| Scapolite group | |
|---|---|
| General | |
| Category | Tectosilicates |
| IMA symbol | Scp |
| Crystal system | Tetragonal |
| Identification | |
| Color | Pink, red, blue, brown, white, grey, colourless, green, yellow, orange, purple |
| Cleavage | Good, in 2 directions |
| Fracture | Conchoidal, uneven, brittle |
| Mohs scale hardness | 5.5–6 |
| Luster | Vitreous |
| Streak | White |
| Diaphaneity | Opaque to transparent |
| Specific gravity | 2.6–2.74 |
| Optical properties | Uniaxial (–) |
| Refractive index | nω = 1.555–1.594 nε = 1.526–1.565 |
| Birefringence | 0.004–0.038 |
| Pleochroism | Moderate to strong |
| Dispersion | 0.017 |
| Ultraviolet fluorescence | Inert to strong pink, orange and yellow |
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