Sanidine

Listed elsewhere for $400. Accepting offers.

This is a blue-green variety of the mineral Sanidine from Itrongay, Madagascar. Sanidine is the high-temperature polymorph of orthoclase and microcline (potassium/K-feldspar).

I have read that the gem-quality feldspar from Madagascar was originally labeled as Orthoclase, but has since been verified to be Sanidine. Also, gem-quality Sanidine crystals have been mined in Madagascar for a very long time, but these blue-green, prismatic crystals seem to have been discovered recently and only came to market between 2024 and 2026.

In the mineral world, it is extremely noteworthy to find a translucent Feldspar crystal, more noteworthy to find a gem-quality one, and even more noteworthy for it to have well-formed, lustrous prism and termination faces. Yet another point of interest is the crystal’s color. Typical for gem-quality Sanidine are shades of yellow or no color at all, and Itrongay is particularly known for its deeply saturated yellow Sanidine. This crystal has a light blue-green color (I believe caused by iron substitution), which, as far as I have been able to find, is completely unique to the Itrongay area.

Dimensions: 2.69 x 1.68 x 1.65 in (6.83 x 4.27 x 4.19 cm)

Weight: 6.51 oz (184.56 g)

Check out my Instagram or TikTok @FantasticFeldspar for more videos and pictures! All photos/videos were taken by me with an iPhone and have not been enhanced. Macro photos/videos taken through a 14x lens.