Labradorite

Hardness: 6-6.5 on Mohs scale. Color: Generally dark base (gray to black) with a vibrant play of iridescent colors (labradorescence) including blue, green, yellow, orange, and red. Luster: Vitreous to pearly. Crystal Structure: Triclinic. Cleavage: Perfect in two directions, creating angles of 86 and 94 degrees. Specific Gravity: 2.68-2.72.

Formation Process: Labradorite forms primarily in igneous rocks such as basalt, gabbro, and anorthosite, crystallizing from magma deep within the Earth. It can also be found in some metamorphic rocks. Geological Age: Varies depending on the host rock, but it has formed throughout various geological eras where appropriate magmatic activity occurred.

Industry/Construction: While less common for large-scale construction, anorthosite rocks rich in labradorite (known as 'black granite') are sometimes used as decorative building stone. Jewelry: Highly prized as a gemstone for its unique play of colors, polished labradorite cabochons are popular in rings, pendants, and earrings. Collecting: Sought after by mineral collectors for its striking optical properties.

Labradorite belongs to the plagioclase feldspar series, which is a continuous series of solid solutions between albite (NaAlSi3O8) and anorthite (CaAl2Si2O8). The spectacular optical phenomenon, labradorescence, is caused by internal lamellar twinning and light interference within the mineral structure. It was first identified in Labrador, Canada.

Field Identification: The most distinguishing characteristic is labradorescence – the strong iridescent play of colors from within the stone when viewed from different angles. It often appears as a dull gray or black rock until rotated to reveal the vibrant flash. Common Locations: Significant deposits are found in Canada (specifically Labrador and Newfoundland), Finland (where a similar gem variety called Spectrolite is found), Norway, Russia, Madagascar, Mexico, and the United States (Oregon). Tips for Collectors: Look for specimens that exhibit strong labradorescence across a large portion of the surface. Polished cabochons best display this phenomenon. Be aware of its perfect cleavage, which means it can be prone to breaking along cleavage planes if mishandled.