garnet: Any of a group of silicateminerals that conform to the generalformula A3B2(SiO4)3. The elementsrepresenting A may include magnesium,calcium, manganese, andiron(II); those representing B mayinclude aluminium, iron(III),chromium, or titanium.
Garnet is a general name for a group of mineralsvarying in color, hardness, toughness, and method of fracture, used for coating abrasivepaper and cloth, for bearing pivots in watches,for electronics, and the finer specimens forgemstones. Garnets are trisilicates of alumina,magnesia, calcia, ferrous oxide, manganeseoxide, or chromic oxide. The general formulais 3R″O·R2O3·3SiO2, in which R″is calcium,magnesium, iron, or manganese, and R″is aluminum,chromium, or iron.
Garnet-coated paper and cloth are preferred to quartz for the woodworking industries,because garnet is harder and gives sharper cuttingedges, but Al2O3 is often substituted forgarnet.
Synthetic garnets for electronic applicationare usually rare earth garnets with a rare earthmetal substituted for the calcium, and iron substitutedfor the aluminum and the silicon.Yttrium garnet, is thus Yt3Fe2(FeO4)3.Yt–Algarnets of 3-mm diameter are used for lasers.Gadolinium (Gd) garnet has been chosen formicrowave use. Gd–Ga garnet made from GdOand GaO is used for computer bubble memories.
