Labradorite
FeldsparJewelryWiki Editorial·4 sources·Reviewed 2026-08-04
A plagioclase feldspar showing labradorescence — the blue-green flash from light interfering between internal lamellae, not from colour in the stone itself.
Properties
| Property | Value | Authority |
|---|---|---|
| Mohs hardness | 6–6½ [1] | — |
| Specific gravity | 2.65–2.75 [1] | — |
| Chemical formula | Na0.5–0.3Ca0.5–0.7Al1.5–1.7Si2.5–2.3O8 The subscripts are ranges, not fixed numbers: labradorite is a plagioclase feldspar, a point on the albite–anorthite series rather than a fixed composition. [4] | — |
| Crystal system | Triclinic [2] | — |
| Common treatments | Receptive to copper diffusion, which GIA says COMPLETELY alters the colour — labradorite and andesine are the two feldspars it names. The treatment is considered permanent, and it is extremely difficult to detect with certainty, only by a qualified laboratory. [3] | — |
Sources
- International Gem Society — reference charts (Mohs hardness, specific gravity, refractive index) — International Gem Society (IGS reference charts)
- Wikipedia — mineral article infoboxes (crystal system) — Wikipedia contributors (Wikipedia mineral infoboxes)
- GIA — An Introduction to Gem Treatments — Gemological Institute of America (GIA, An Introduction to Gem Treatments (Robert Weldon))
- Handbook of Mineralogy — Mineral Data Publishing / Mineralogical Society of America (Handbook of Mineralogy, Mineral Data Publishing)