Andesine-Labradorite

Andesine-labradorite is an intermediate member of the plagioclase feldspar series, sitting between andesine and labradorite in calcium content. As a gem it became prominent in the 2000s under the trade name andesine, offered in striking red, orange, champagne, and green colors.

The gemstone gained notoriety because much of the red and green material sold was copper-diffusion treated - colorless or pale feldspar artificially colored by diffusing copper at high temperature - and some was misrepresented as natural. Genuinely natural copper-bearing red feldspar (like Oregon sunstone) does exist but is far rarer.

The stone is transparent to translucent, takes a bright polish, and can show schiller or aventurescence when copper platelets are present.

As a plagioclase, andesine-labradorite crystallizes from intermediate to mafic magmas - andesite, diorite, and gabbro - where calcium and sodium share the feldspar structure. Naturally copper-colored sunstone variants form in basaltic lava flows, as in Oregon.

Much of the commercial red and green andesine, however, originates as pale feldspar from Inner Mongolia, China, or Tibet that is then artificially treated. The geological debate over claimed Tibetan and Congolese deposits of naturally red andesine has been a long-running controversy in the gem trade, with field studies casting doubt on several claimed sources.

Andesine-labradorite is a feldspar: hardness 6-6.5, vitreous luster, white streak, and two cleavages near 90 degrees, often with fine albite-twin striations. Gem colors range from red and orange to green and champagne.

Distinguishing natural from copper-diffusion-treated stones is difficult and usually requires a gemological laboratory, which looks for unnatural color zoning, copper concentration gradients near the surface, and treatment indicators. Buyers should treat unusually saturated, inexpensive red or green andesine with caution and seek lab reports. It can resemble sunstone, but sunstone shows metallic copper spangles.

Andesine-labradorite is used almost entirely as a faceted gemstone for rings, pendants, and collector stones, valued for warm red-orange hues reminiscent of fine sunstone or imperial topaz at lower cost.

Because of widespread treatment and disclosure problems, its market value depends heavily on whether color is natural and disclosed; treated stones are inexpensive, while genuinely natural copper-bearing red feldspar commands much more. Always insist on disclosure of treatment. It has no distinct metaphysical lore beyond general feldspar and sunstone associations of warmth and vitality.