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Moonstone

Feldspar

By Tim Matthews, JD, FGA, GG, DGA,
CEO and President of JTV
Published: June 2014
Modified: March 2023
Moonstone Polished Moonstone Rough Moonstone Jewelry
Table of Contents
  • General Information
  • Moonstone Colors
  • Alternate Names
  • Countries of Origin
  • Care
  • Species/Variety

Moonstone is the phenomenal variety of feldspar that shows adularescence, a soft billowy sheen that rolls over the surface of the stone. Adularescence is an interference effect caused by alternating internal layers of albite and orthoclase feldspar. When the phenomena displays a blue sheen in fine colorless labradorite feldspar it is called “rainbow moonstone”. The adularescent orthoclase feldspar from the Adular Mountains of Switzerland is called adularia.

General Information

  • Classification
  • Optical Properties
  • Characteristic Physical Properties
  • Chemistry & Crystallography
Common Name
Moonstone
Species
Feldspar
Transparency
Transparent - Translucent
Refractive Index
1.518-1.568
Birefringence
0.005-0.011
Optic Character
Biaxial
Optic Sign
Positive or Negative
Polariscope Reaction
Doubly Refractive (DR)
Fluorescence
SWUV: inert to weak pink to red or orange, weak pinkish orange
LWUV: inert to weak yellowish white, blue, moderate chalky blue, pink or red
Pleochroism
Unobservable
Hardness
6-6.5
Streak
White
Specific Gravity
2.520-2.750 Range:+/-0.05 Typical:2.690
Toughness
Poor
Inclusions
Moonstone occasionally contains colorless inclusions and might show parallel multiple twinning planes.
Luster
Vitreous
Fracture
Uneven, Splintery
Cleavage
Perfect, in two directions
Chemical Name
calcium, sodium aluminum silicate
Chemical Formula
NaAlSi3O8 and CaAl2Si2O8
Crystal System
NA
Chemistry Classification
Silicate

Moonstone Colors

  • Orange Moonstone
    Orange
  • Red Moonstone
    Red
  • Gray Moonstone
    Gray
  • Pink Moonstone
    Pink
  • Orange Moonstone
    Orange
  • Brown Moonstone
    Brown
  • Black Moonstone
    Black
  • Brown Moonstone
    Brown
  • Multi-color Moonstone
    Multi-color
  • Yellow Moonstone
    Yellow
  • White Moonstone
    White

Alternate Names

Rainbow Moonstone, Star Moonstone

Countries of Origin

Tanzania, United Republic Of; Myanmar; Russian Federation; Sri Lanka; United States of America; Madagascar; Switzerland; French Polynesia; India; Mozambique; Unknown; Malawi; China; Brazil

Care

Normal care

Species/Variety

Blue Moonstone

Blue moonstone is the finest variety of labradorite moonstone. It is highly transparent and displays strong blue adularescence. The best specimens originally came from Myanmar (formally known as Burma), but it can also come from India, Madagascar, Malawi, Sri Lanka and Tanzania.

Blue Moonstone Moonstone
Blue Moonstone Moonstone
  • Classification
  • Optical Properties
  • Characteristic Physical properties
Common Name
Blue Moonstone
Birefringence
0.009
Specific Gravity
2.650
Toughness
Poor
Inclusions
Moonstone occasionally contains colorless inclusions and might show parallel multiple twinning planes.
Stability
Good

Moonstone-Labradorite

Labradorite moonstone is a variety of feldspar that displays an amazing optical phenomenon called adularescence. Labradorite is a plagioclase feldspar and a member of the triclinic crystal system. Internally repeating feldspar layers scatter the light that enters the stone creating a mystical glow reminiscent of moonbeams. This glow comes to life, rolling across the gems surface, when it is moved. Labradorite moonstone comes in colorless, white, slight orange or green with a blue sheen. Adularescent labradorite with a multi-colored glow is sometimes called Rainbow Moonstone.

Moonstone-Labradorite Moonstone
Moonstone-Labradorite Moonstone
  • Classification
  • Optical Properties
  • Characteristic Physical properties
Common Name
Moonstone-Labradorite
Birefringence
0.009
Specific Gravity
2.650
Toughness
Poor
Inclusions
Moonstone occasionally contains colorless inclusions and might show parallel multiple twinning planes.
Stability
Good

Moonstone-Orthoclase

Orthoclase moonstone is a variety of feldspar that displays an amazing optical phenomenon called adularescence. Orthoclase feldspar is a member of the monoclinic crystal system. Internally repeating feldspar layers scatter the light that enters the stone creating a mystical white glow reminiscent of moonbeams. This glow comes to life, rolling across the gems surface, when it is moved. It can be colorless to white, orange, yellow or brown.

Moonstone-Orthoclase Moonstone
Moonstone-Orthoclase Moonstone
  • Classification
  • Optical Properties
  • Characteristic Physical properties
Common Name
Moonstone-Orthoclase
Refractive Index
1.518-1.526 Tolerance:(+0.010/-0.010)
Pleochroism
Typically none
Specific Gravity
2.550
Toughness
Poor
Inclusions
Moonstone will have blue or white adularescence. Stones might have centipede like inclusions and material with aventuresence or asterism might contain reflective inclusions such as fine needles or elongated hematite platelets.
Stability
Good

Rainbow Moonstone

Adularescent labradorite with a multi-colored glow is sometimes called rainbow moonstone. Rainbow moonstone is colorless and highly transparent and it displays an amazing optical phenomenon called adularescence. Labradorite is a plagioclase feldspar and a member of the triclinic crystal system. Internally repeating feldspar layers scatter the light that enters the stone creating a mystical glow reminiscent of moonbeams. This glow comes to life, rolling across the gems surface, when it is moved.

Rainbow Moonstone Moonstone
Rainbow Moonstone Moonstone
  • Classification
  • Optical Properties
  • Characteristic Physical properties
Common Name
Rainbow Moonstone
Birefringence
0.009
Specific Gravity
2.650
Toughness
Poor
Inclusions
Moonstone occasionally contains colorless inclusions and might show parallel multiple twinning planes.
Stability
Good

Adularia

Adularia is a variety of feldspar found in hydrothermal veins in mountainous areas, from one of which it derives its name: the Adular Mountains of Switzerland. It commonly forms colorless to white, cream, pale yellow to pink, or reddish-brown, glassy, prismatic, twinned crystals. These transparent to colorless gems often display a white to blue sheen.

Adularia Moonstone
Adularia Moonstone
  • Classification
  • Characteristic Physical properties
Common Name
Adularia
Specific Gravity
2.520
Toughness
Poor
Inclusions
Adularia will display white or blue adularescence. Stones might have centipede like inclusions and material with aventuresence or asterism might contain reflective inclusions such as fine needles or elongated hematite platelets.
Stability
Good
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