Class: Phosphates, arsenates, vanadates
Group: Amblygonite
Original description: Des Cloizeaux, A., 1871. Note sur la Montebrasite — Comptes Rendus Hebdomadaires des Séances de l’Académie des Sciences 73: 306 [
view in ‘Library’].
Type locality: Montebras mines, Montebras, Soumans, Creuse, Nouvelle-Aquitaine, France (Des Cloizeaux, 1871: 306).
Type material: unknown.
Etymology: for the type locality, Montebras, France.
Distribution: Brazil: Minas Gerais; Canada; France; Sweden; USA (
Anthony et al., 2001—2005).
Chemistry
LiAl(PO4)(OH)
Essential elements: hydrogen (H), lithium (Li), oxygen (O), aluminium (Al), phosphorus (P).
Crystal data
Crystallography: triclinic — pinacoidal.
Crystal habit: crystals typically equant, may be short to long prismatic, to 10 cm; as coarse cleavable or blocky to rounded nodular masses.
Twinning: common on {111}, producing tabular composite crystals (
Anthony et al., 2001—2005).
Optical properties
Colour: pale brown, pink, pale yellow, grey, white, colourless; colourless in transmitted light (
Anthony et al., 2001—2005).
Diaphaneity: transparent to translucent (
Anthony et al., 2001—2005).
Lustre: vitreous, pearly on cleavages (
Anthony et al., 2001—2005).
Refractive index: 1.594—1.646 — anisotropic [biaxial (+/-)] (
Anthony et al., 2001—2005).
Birefringence: 0.022—0.03.
Dispersion: no data.
Pleochroism: none.
Material from ‘Repository’