Oregon sunstone : a flaming stone

The Oregon Sunstone was designated Oregon’s Official State Gem by the Oregon legislature in 1987.

What is the sunstone made of?

Sunstone is a member of the feldspar family. Feldspars are the most abundant minerals in the earth's crust. They are, for example, part of the composition of granite, quarts and mica, but they are also found as gemstones.

1. Calc-sodium feldspars or plagioclases (very low in potassium)
2. The alkaline feldspars (very poor in calcium)

Among the calcosodic feldspars or plagioclases, we find minerals very important in gemology as andesine, labradorite and oligoclase that can often be found in commerce as moonstone or sunstone. (Thoreux E., 2019, p.4).

Oregon sunstone is a natural cupriferous feldspar of the labradorite type. Its colours vary depending on the presence of copper in its crystal structure (Pay & Al., 2013). The more copper within the stone, the darker the complexion. Although a large amount of sunstones are pale yellow-pink, some of them show a dichroism from red to green.

How did the Oregon Sunstones come to be?

Oregon's Sunstones are found in a volcanic environment. A major volcanic episode 15 to 17 million years ago revealed the sunstones found today as phenocrysts in ancient, highly porphyritic lava flows. It is hypothesized that these gems were formed in magma chambers caused by magmatism generated by the meeting of two tectonic plates and then expelled by volcanoes and/or stratovolcanoes (Pay & Al., 2013).

Did you know that...According to a legend of the Native peoples of Oregon, a major battle took place near the Ochocos Mountains in Oregon. A brave warrior was pierced by an arrow and his blood flowed onto the sunstone fragments. The blood being inhabited by the spirit of this great warrior, it would then impregnate these stones in order to color them with a powerful and sacred red (Thoreux E., 2019).

References:

Pay & Al. (2013). Three Occurrences of Oregon Sunstone. Gem & Gemology, 49(3). Repéré à https://www.gia.edu/gems-gemology/fa13-oregon-sunstone-pay

Thoreux E. (2019). L’Oregon Sunstone ou la renaissance d’un phénix. Revue de l’Association Française de Gemmologie, 207(1). Repéré à https://oregonsunstoneguide.com/assets/revue-afg-207.pdf