Class: Phosphates, arsenates, vanadates
Group: Amblygonite
Original description: ‘Amblygonit’ Breithaupt, J. F. A., 1818. Gattung B. Amblygonit — Handbuch der Mineralogie von C. A. S. Hoffmann, Craz und Gerlach, Freiberg 4: 159—161 [
view in ‘Library’].
Type locality: Chursdorf, Penig, Chemnitz, Saxony, Germany.
Type material: Technische Universität Bergakademie, Freiberg, Germany, 20336 (
Anthony et al., 2001—2005).
Etymology: derived from the Greek words
αμβλύς (amvlys) ‘blunt’ and
γωνία (gonia) ‘angle’, referring to the fact that its cleavage angle slightly differs from 90°, distinguishing it from scapolite for which it was originally mistaken.
Distribution: Brazil; Canada: Manitoba, Bernic Lake; Germany: Saxony, Chemnitz, Penig, Chursdorf; Mozambique: Zambezia, Alto Ligonha district; Namibia: near Karibib; USA: Maine, Oxford Co., at Hebron (
Anthony et al., 2001—2005).
Chemistry
(Li,Na)Al(PO4)(F,OH)
Essential elements: hydrogen (H), lithium (Li), oxygen (O), fluorine (F), sodium (Na), aluminium (Al), phosphorus (P).
Crystal data
Crystallography: triclinic — pinacoidal.
Crystal habit: crude crystals, typically equant with complex form development, to 1.5 m; massive.
Twinning: on several laws, with microscopic polysynthetic twinning common (
Anthony et al., 2001—2005).
Optical properties
Colour: milk-white, pale yellow, beige, salmon-pink, pale green, pale blue, grey, may be colourless; colourless in transmitted light (
Anthony et al., 2001—2005).
Diaphaneity: transparent to translucent (
Anthony et al., 2001—2005).
Lustre: vitreous to greasy (
Anthony et al., 2001—2005).
Refractive index: 1.578—1.646 — anisotropic [biaxial (+/-)] (
Lazzarelli, 2012).
Birefringence: 0.02—0.03.
Dispersion: 0.015 (low).
Pleochroism: none (
Arem, 1987: 40).
Material from ‘Repository’