Sunstone is a gem-quality member of the feldspar group of minerals.
It is famed for its aventurescence, often referred to as ‘schiller’.
Sunstone may also be traded as ‘aventurine feldspar’, but nowadays, the term ‘aventurine’ is primarily used only in reference to the green quartz known as ‘aventurine’.
Not all sunstone exhibits strong aventurescence or schiller.
The intensity of the optical phenomenon depends upon the size of inclusions, which are typically composed of hematite or goethite.
Smaller inclusions tend to exhibit more sheen, while larger inclusions generally appear as glittery, spangled metallic reflections.