Mineral Information and Data:

(Ca,Na)4(Si,Al)12O24(CO3,SO4,Cl) [CNMNC approved formula]

Named from the Greek for "less", referring to its less acute pyramidal form compared with vesuvianite.

IMA status : Valid species (Pre-IMA 1801) Grandfathered
(8th edition) :  
  (76) Tectosilicate Al-Si Framework
  (76.03) Framework with other Be/Al/Si frameworks
  (76.03.01) Scapolite group
(10th edition) :
  (09) Silicates
  (09.F) Tektosilicates without Zeolitic H2O
  (09.FB) Tektosilicates with additional anions
Crystal system: Tetragonal System
Point group (H-M): 4/m — dipyramidal
Space group: I4/m
Unit cell: a = 12.179(1) Å, c = 7.571(1) Å, Z=2
Crystal Habit: Crystals prismatic, typically with flat pyramidal terminations, striated || [001], to 0.7 m; granular, massive.
Color: Colorless, white, grey; pink, violet, blue, yellow, orange-brown, brown; colorless in thin section
Diaphaneity: Transparent to opaque
Luster: Vitreous to pearly or resinous
Hardness (Mohs): 5 - 6
Measured Density: 2.74 - 2.78 g/cm3
Cleavage: {100}, {110}, distinct
Tenacity: Brittle
Fracture: Uneven to conchoidal
Streak: White
Polymorphism and Series: Forms a series with marialite; intermediate members are P42/n
Geologic Setting: Typically in regionally metamorphosed rocks, especially marbles, calcareous gneisses, granulites, and greenschists. Also in skarns, some pegmatites, pneumatolytically or hydrothermally altered mafic igneous rocks, and ejected volcanic blocks.
Mineral Association: Plagioclase, garnet, pyroxenes, amphiboles, apatite, titanite, zircon
Luminescent Properties: Commonly fluoresces orange to bright yellow or red under LW or SW UV or both.
Other Properties: Gemstone Readily Available.


Origin: Monte Somma (Vesuvius), Campania, Italy
Sample size: Microscopic image
Photo and Owner: Lou Perloff


Origin: Bear Lake, Quebec, Canada
Sample size: 5.8 x 3.8 x 2.7 cm
Photo: Dan Weinrich


(zoom-in of above)