This month I’m going to tell you about an interesting but not particularly common gemstone – ruby in zoisite.
Ruby in zoisite was discovered in 1954 in Tanzania, Africa, and so far, this is the only location it has been found. Other names for this gem are “anyolite” (from the Masai word “anyoli,” meaning green) and “Tanganyika artstone.”
Ruby in zoisite is a rock that is comprised of 3 minerals: corundum (red), zoisite (green), and hornblende (black). The colors can be so bright that it is hard to believe it’s a natural stone. The rough stone can be difficult to work with because of the differences in hardness of the constituent minerals. Ruby (corundum) has a hardness of 9 on the Mohs scale of mineral hardness, while zoisite is 6-7 and hornblende is 5-6. Ruby in fuchsite looks similar to ruby in zoisite, but it lacks the black hornblende. In addition, fuchsite is a mica and is very soft (2-3 on the Mohs scale) which makes it less desirable for use in jewelry.
Zoisite comes in a variety of colors including colorless, violet-blue, grey, yellow, brown, pink, and green. The violet-blue colored zoisite is better known as Tanzanite, also only found in Tanzania, Africa. Another zoisite gem you may have heard of is thulite, the opaque, pink variety.
Ruby from this source is opaque and not good for cut gems. Ruby crystals tend to be very dark pink to red and often show the hexagonal outline of the crystal. The ruby inclusions can vary greatly in size from just small specks of red to crystals several inches across (see photo above).
Ruby in zoisite is often used in carvings that make use of the arrangement of the colorful minerals. The color combination in ruby in zoisite isn’t for everyone, but if you like it, it makes for very striking and unique pieces of jewelry.