Another variety more frequently used as a gemstone is the aventurine-feldspar or sun-stone found as reddish cleavage masses in gneiss at Tvedestrand in southern Norway; this presents a brilliant red to golden metallic glitter, due to the presence of numerous small scales of hematite oriented within the feldspar structure.

It occurs in porphyry and diabase dikes and sills as well as in the volcanic rocks andesite and trachyte, and in mugearite where its presence is a defining feature.

The best developed and largest crystals are those found with orthoclase, quartz, epidote, and calcite in veins in granite at Arendal in Norway.

Some examples are called moonstone and show Schiller iridescence due to the presence of exsolution lamellae on cooling in the peristerite miscibility gap, ~An5-An18.

One of the iridescent varieties of oligoclase, discovered in 1925 near the White Sea coast by academician Alexander Fersman, became widely known under the trade name belomorite.