This is the labradorite sphere with irisation in blue colors. Diameter 1.9″ (49mm). Weight – 6oz (170 grams). Origin: Russia, Transbaikalia.
Some information about labradorite:
Labradorite, a feldspar mineral, is an intermediate to calcic member of the plagioclase series. It has an anorthite percentage (%An) of between 50 and 70. The specific gravity ranges from 2.68 to 2.72. The streak is white, like most silicates.
Labradorite occurs in mafic igneous rocks and is the feldspar variety most common in basalt and gabbro. The uncommon anorthosite bodies composed almost entirely of labradorite. It also found in metamorphic amphibolites and as a detrital component of some sediments. Common mineral associates in igneous rocks include olivine, pyroxenes, amphiboles and magnetite.
Labradorite can display an iridescent optical effect (or schiller) known as labradorescence. The term labradoresence coined by Ove Balthasar Bøggild. Some gemstone varieties of labradorite exhibiting a high degree of labradorescence are called spectrolite.