Sunstone is a kind of plagioclase feldspar that glitters with stunning brightness in a similar manner as Aventurine does. In order not to be confused with this Quartz counterpart, it is sometimes referred to as aventurine feldspar. While Aventurine is mainly green in color, Sunstone is available in a number of colors such as yellow, brown, copper schiller, green, blue and orange. It can also be colorless. It is called the sunstone because of the spangled shades of brown, red, orange and gold that it emits when viewed from a certain direction. This gemstone is seen in many states of the United States of America as well as in Russia, Madagascar, India, Sweden and Southern Norway.
It is a semitransparent-opaque gemstone with a refractive index of 1.539-1.547. Though sunstone is available in different types such as Star sunstone and Oregon sunstone, it is chemically represented by the formula (Ca, Na)((Al, Si)2Si2O8). Belonging to the mineral class of oligoclase or microcline, this sparkling gemstone has vitreous luster with basal, prismatic and pinacoidal cleavage planes of 2,1, 2,1, and 3,1 respectively. It is a tough stone with a Mohs hardness of 6 – 6.5 and a specific gravity of 2.62 – 2.65. Set in a triclinic crystal system, Sunstone has a double refraction of 0.01 and birefringence of 0.007 – 0.01.
With a surface giving an optical effect referred to as shiller, this hard stone stands out from other stones in the feldspar family. This effect is a result of the presence of copper in the composition of the stone. Calcium aluminum silicate, as it is chemically called, contains tiny greenish platelets of hematite or goethite which may be golden or reddish in some deposits. It has good stability and splintery and uneven fracture.
Sunstone is an invaluable stone in lapidary and jewelry making industries. Both in ancient times and in today’s society, many pieces of jewelry have used this stone either alone or in a combination of gemstones to make ornamental objects, bracelets, and necklaces. The transparent forms can be cut and polished to produce valuable rings and earrings, thus making it a stone with an inestimable value in the fashion industry.