Spinel

Spinel is a gemstone with a wide array of colors that was recently added as an August birthstone. While not one of the "big four" gemstones, it is well-known and gaining popularity due to its beauty.

The data below provides basic information, but gahnite and gahnospinel generally have slightly higher refractive indices. Furthermore, popular varieties like Vietnamese cobalt spinel and Tanzanian Mahenge spinel mesmerize many with their beauty. In recent years, stones with good color have become truly expensive, with red, hot pink, and beautiful blue colors particularly impacting the price.

It is also said that pure yellow spinel basically does not exist, though it may appear yellow due to inclusions. In addition, there are also taaffeite and musgravite, which are very similar to spinel.

Name: Spinel
Japanese Name: Senshou-seki (尖晶石)
Chemical Composition: MgAl₂O₄
Crystal System: Isometric (Cubic)
Specific Gravity: Approx. 3.55 ± 0.05
Mohs Hardness: 7.5
Cleavage: None
Luster: Vitreous
Transparency: Transparent to Opaque
Refractive Index: 1.712 to 1.736
Birefringence: None
Color: All colors except yellow
Dispersion: 0.020 ± 0.003