Next on our list of feldspar gemstones, we have the stellar, spangled counterpart to the moonstone: sunstone! 

History and Meaning

The sunstone has found itself taking the spotlight (or sunlight) in many old legends revolving around the sun. Ancient Greeks believed that it embodied the radiance of the sun god Helios. Others, like the vikings believed the stone could be used to locate the sun in an overcast and snowy sky by holding it up and taking note of where it casts a beam of light. Though, this “sunstone” may not be the sunstone we’re familiar with. Rather, it may be Iceland spar, a transparent variety of calcite that can polarise light.

Oregon sunstones in particular also have a legend surrounding them. It is said that the blood of a warrior coated these suntones, infusing them with the warrior spirit and sacred power that manifests in its striking shades of red. 

Colours

Sunstones can come in many colours, often in warmer shades like red, orange or yellow. Unlike the sun, they can come in green as well as multiple colours! 

Multicoloured Oregon sunstone
https://www.johndyergems.com/oregon-sunstone-gemstone-info.html

Properties 

Sunstones exhibit aventurescence, an optical phenomenon that causes the stone to sparkle in the light. It is caused by tiny, flaky inclusions of reflective materials inside the stone. 

Like other feldspars, sunstones have a hardness between 6 and 6.5. Sunstones are primarily defined by its appearance rather than its chemical composition. As such it can have different amounts of elements, like orthoclase (high potassium), oligoclase (high sodium) or even plagioclase (slightly higher calcium). Their defining property is their aventurescence rather than any particular feldspar composition. In fact, Oregon sunstones are labradorites (another type of feldspar used as a gemstone!) that exhibit the sunstone’s characteristic aventurescence from tiny amounts of copper impurities in its structure.

Location 

Sunstones can be found in the USA where predictably, the famous Oregon sunstone is found in the state of Oregon. They can also be found in other continents, like Brazil and Mexico in South America, India and China in Asia, or Tanzania and Congo in Africa.

Fun Facts 

Other than the copper, other reflective impurities like hematite, pyrite and goethite can cause aventurescence in sunstones!

Meet the writer : I’m ZX, a former intern at The Gem Museum. My interest in chemistry makes me especially curious about the chemistry behind gems, though I also enjoy exploring their hidden history.