Garnet as gemstones. The gemstone varieties occur in shades of green, red, yellow, and orange. In the US it is known as the birthstone for January. It is the state mineral of Connecticut, New York's gemstone, and star garnet (garnet with rutile asterisms) is the state gemstone of Idaho. Garnet sand is a good abrasive, and a common replacement for silica sand in sand blasting. Alluvial garnet grains which are rounder are more suitable for such blasting treatments. Mixed with very high pressure water, garnet is used to cut steel and other materials in water jets. For water jet cutting, garnet
Yttrium aluminium garnet has low heat sensitivity. As a synthetic gemstone YAG has numerous varietal and trade names, as well as a number of misnomers. Synonymous names include: "alexite", "amamite", "circolite", "dia-bud", "diamite", "diamogem", "diamonair", "diamone", "diamonique", "diamonite", "diamonte", "di'yag", "geminair", "gemonair", "kimberly", "Linde simulated diamond", "nier-gem", "regalair", "replique", "somerset", "triamond", "YAIG", and "yttrium garnet". Production for the gem trade decreased after the introduction of synthetic cubic zirconia; there was little production. Some demand exists as synthetic garnet, and for designs where the very high refractive index of cubic zirconia is not desirable. Neodymium-doped YAG (Nd:YAG) was developed in the early 1960s, and