Sunstone: Gemstone Information
The Name Sunstone was originally coined for near colourless oligoclase feldspar in which aligned red or orange platy hematite (and/or goethite) inclusion (platelets may be so numerous that they also influence the material’s body colour) that produced a specular reflectance or spangle effect that was named aventurescence (a sort of schiller but more scintillating). Light interference on hematite or goethite plates can also result in green or blue colours. Over time, aventurescent plagioclase feldspars with compositions other than oligoclase and/or inclusions other than hematite were discovered.
In each instance the name sunstone was also applied. Thus by common usage the name sun stone has come to mean any aventurescent feldspar. Attempts to preserve the original definition of sunstone and adopt the term ‘heliolite’ for other aventurescent feldspars have, by force majeure, failed to gain acceptance.
The red copper-bearing, mainly labradorite (but bytownite, andesine and oligoclase have all been reported), plagioclase from Oregon that exhibits aventurescence/schiller was so dealt with; the name labradorite all but being ousted except when applied to the dark grey massive material. The sunstone name was further extended to incorporate material without aventurescence/schiller and even subsumed non-red material: presumably arising from the success of product branding. Similar stones from other localities worldwide have likewise been named sunstone. Given this scope for variation a range of properties, chemistry and features for sunstone exists.