What is Sunstone?
Sunstone is an aventurescent feldspar gem variety whose lively metallic glitter comes from reflective inclusions, making it popular with jewellery designers, carvers and collectors.
Mineralogy and crystal structure
Reference formula: (Na,Ca)(Al,Si)AlSi2O8. Sunstone is a feldspar variety rather than a separate ideal species. The displayed model is a labelled representative albite/plagioclase structure; aventurescence depends on inclusions such as copper or hematite and should not be confused with surface glitter treatment. Sunstone is classified with silicates and has a triclinic crystal system. Typical hardness is 6–7 on the Mohs scale and specific gravity is approximately 2.6–2.8.
Colour, lustre and habit
Typical colours include orange, red, green, yellow, colourless, brown. The usual granular, tabular, massive habit and vitreous lustre help describe a specimen, but colour alone is not diagnostic.
Formation and notable localities
Sunstone forms in or is associated with alkali feldspar-rich volcanic rocks, pegmatites, basaltic environments and alluvial deposits. Important documented localities include Oregon in the United States, India, Tanzania, Norway, Canada and Madagascar.
A gemstone that flashes like sunlight
Sunstone sells through optical movement: aventurescent platelets catch light as the stone turns. Colour, transparency, inclusion pattern and locality create very different commercial grades.
Collecting and care
Avoid strong impact, acids and sudden heat. Clean gently with mild soapy water and disclose stabilisation, coatings or other treatments when selling.
