Scapolite

Scapolite group
General
CategoryTectosilicates
IMA symbolScp[1]
Crystal systemTetragonal
Identification
ColorPink, red, blue, brown, white, grey, colourless, green, yellow, orange, purple
CleavageGood, in 2 directions
FractureConchoidal, uneven, brittle
Mohs scale hardness5.5–6
LusterVitreous
StreakWhite
DiaphaneityOpaque to transparent
Specific gravity2.6–2.74
Optical propertiesUniaxial (–)
Refractive indexnω = 1.555–1.594
nε = 1.526–1.565
Birefringence0.004–0.038
PleochroismModerate to strong
Dispersion0.017
Ultraviolet fluorescenceInert to strong pink, orange and yellow

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)[2] and marialite (Na4Al3Si9O24Cl).[3][4] Silvialite (Ca,Na)4Al6Si6O24(SO4,CO3) is also a recognized member of the group.[5][4][6]

  1. ^ Warr, L.N. (2021). "IMA–CNMNC approved mineral symbols". Mineralogical Magazine. 85 (3): 291–320. Bibcode:2021MinM...85..291W. doi:10.1180/mgm.2021.43. S2CID 235729616.
  2. ^ Meionite data on Webmineral
  3. ^ Miarialite data on Webmineral
  4. ^ a b Scapolite group on Mindat.org
  5. ^ Silvialite data on Webmineral
  6. ^ Teertstra, D. K.; Schindler, M.; Sherriff, B. L.; Hawthorne, F. C. (1999). "Silvialite, a new sulfate-dominant member of the scapolite group with an Al-Si composition near the 14/m–P42/n phase transition". Mineralogical Magazine. 63 (3): 321–329. Bibcode:1999MinM...63..321T. doi:10.1180/002646199548547. ISSN 0026-461X. S2CID 129588463.