"Volga Blue Granite" - coarsely-crystalline anorthosite from the Precambrian of Ukraine.
Anorthosites are uncommon intrusive igneous rocks almost exclusively composed of Ca-rich plagioclase feldspar. There’s usually a blackish pyroxene component as well. Anorthosites having labradorite plagioclase feldspar will display a wonderfully colorful iridescent play of colors (labradorescence). This makes them desirable decorative stones.
The dark, very coarsely-crystalline anorthosite shown above is from Ukraine. It is remarkable in having obvious zoned plagioclase feldspar. This is from the Volodarsk-Volhynsky Intrusion in the southern Korosten Complex, a large igneous suite intruded through the Ukrainian Shield. The Volodarsk-Volynsky Intrusion dates to the late Paleoproterozoic (1.758-1.760 Ga). This material is quarried between the cities of Korosten and Zhitomir, central Zhitomir Province, northwestern Ukraine.