Mindblown: a blog about philosophy.

Spinel is magnesium aluminum oxide, in which magnesium can be partly or completely replaced by iron, zinc, or manganese. Spinel was considered an individual mineral only 150 years ago. Before that it was classified as ruby. It is believed spinel got its name from the Latin spina, meaning a thorn, in reference to its sharply…

This beautiful blue stone has a high content of sodium. Sodalite is member of the feldspathoid group of minerals; which are similar to feldspar but with less content of silica. It occurs in syenite and trachyte rocks, as well as pegmatite. It is also found in volcanic ejecta and in contact metamorphosed limestones and dolomites.…

Any color of corundum other than red is called sapphire. Sapphire’s name derives from the Greek “blue.” Sapphires can be blue, black, purple, violet, dark blue, bright blue, light blue, green, yellow, and orange. Colorless sapphire is called leuko-sapphire, name deriving from the Greek “white;” pinkish orange sapphire called Padparadscha, which is a Sinhalese word…

Ruby is the red variety of the mineral corundum, an oxide of aluminum. It has a purplish-bluish red to yellow-red color. The finest color of ruby is pure red with a hint of blue, which is called “pigeons blood.” The substance that provides the color in ruby is chromium, and in the case of brownish…

Rose quartz is a variety of crystalline quartz. Rose quartz is a pale pink to deep peachy pink color gemstone. It is rarely found in crystals, and when these occur, they seldom exceed ½ or (1 cm) in length. Its coloration has been attributed to traces of titanium, while its milky appearance may be due…

Rhodochrosite was named in 1800, its name derives from the Greek rhodokhros, meaning “of rosy color.” It is a manganese carbonate found in hydrothermal ore veins formed at moderate temperatures, in high-temperature metamorphic deposits, and as a secondary mineral in sedimentary manganese deposits. Gem-quality transparent rhodochrosite crystals have a bright pink color. They occur in…

Pyrite is also known as “fool’s gold.” Pyrite’s name derives from the Greek word pyr, meaning “fire,” due to the sparks it emits when struck by iron. It is also called iron pyrite or simply pyrites. Pyrite is hard, brittle and often crystalline. Pyrite occurs in igneous rocks, and is found in hydrothermal veins associated…

Peridot is the name variety of the mineral olivine.  It is believed that the name derives from the Arabic word faridat, meaning gem.  Peridot has been mined for over 3,500 years on the former John’s Island in the Red Sea, now called Zabargad Island and is located in Egypt. The Greek name chrysolite, meaning gold…

The word opal derives from the Indian word “stone.” There are three categories for opal; precious opals, yellow fire opals, and common opals. The special characteristics of opal are their play of color, a display of rainbow like hues which changes with the angle of observation. Opal is a form of silica but different from…

Obsidian is a natural volcanic glass that forms when lava solidifies so rapidly that mineral crystals do not have time to grow. Its color is usually black, but sometimes with the presence of hematite (iron oxide) it can be Indian red to brown. Obsidian has a bright, vitreous luster on smooth surfaces, and is sometimes…