Moonstone (gemstone)

Not to be confused with Moon rock.
For other uses, see Moonstone (disambiguation).
Moonstone
General
CategoryAnorthoclase variety
Formula
(repeating unit)		(Na,K)AlSi3O8
Crystal systemMonoclinic
Identification
ColorCan be numerous colors, including blue, grey, white, pink, peach, green and brown, as well as colorless
Cleavageperfect
Fractureuneven to conchoidal
Mohs scale hardness6.0
LusterOpalescent
Streakwhite
Specific gravity2.54–2.66
Optical propertiesfor orthoclase and sanidine, biaxial (–); for oligoclase, biaxial +/–
Refractive index1.518–1.547
Birefringence0.005–0.01
Dispersion0.012
A small rough moonstone sample

Moonstone is a sodium potassium aluminium silicate ((Na,K)AlSi3O8) of the feldspar group that displays a pearly and opalescent schiller.[1][2] An alternative name for moonstone is hecatolite[2] (from goddess Hecate).

  1. ^ Cite error: The named reference Gemsoc was invoked but never defined (see the help page).
  2. ^ a b Moonstone, Mindat.org, retrieved 2022-02-06