Spinel semiprecious gemstone index and mineral information

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 pointed crystals. Red spinel is known as “Balas ruby,” named after a place in northern India where the stones were thought to be found.

Spinel is an important gemstone, although it is overshadowed by ruby and sapphire. Deep reds of spinel demand a high price, whereas the paler shades of red, brownish and yellowish reds are much cheaper. The red rose, pink and yellow to orange spinel is called rubicelle; purple spinel is called almandine spinel, and blue or dark green to black spinel is calle pleonast. Pale to deep blue, violet blue, purple and mauve are also other colors of spinel and are also important. Black spinels have been found on the volcano Vesuvious in Italy.

Spinel is usually found in alluvial deposits such as those of Burma and Sri Lanka. Spinel forms in plutonic and metamorphic rocks. It is associated with olivine, phlogoite, and chondrodite in hornfels and marbles of metamorphic rocks. Iron rich spinels are called ceylonites and zinc-rich spinels are termed gahnospinels. Spinel is made synthetically where it is colored to imitate other gemstones such as aquamarine and zircon.

The best gem spinels are found in Ceylon and Burma, although small colorful stones have been found at several places in the United States such as California, New Jersey, New Mexico, and North Carolina.

Mohs’ hardness: 7.5 – 8