Gemstone Glossary

Milarite

Milarite is a rather rare mineral often found in a muted green or yellow shade and forming good prismatic hexagonal crystals. It is named for its locality of first discovery; Val Giuf (Val Milar), Tavetsch, Grischum, Switzerland.

Milarite belongs to the Milarite-Osumilite mineral group, which is sometimes referred to as simply the Osumilite group, or the Milarite group. The group is composed of at least 18 rather rare mineral varieties. Only Milarite; Osumilite; and Sugilite are somewhat well known minerals from this group. All the others are extremely rare in occurrence.



Milarite is composed of Hydrated Potassium Calcium Aluminum Beryllium Silicate (K2Ca4Al2Be4 Si24O60-H2O). It ranks 5.5 to 6 on the Moh’s Scale of Hardness with a Specific Gravity of 2.5 to 2.6. Milarite crystals are commonly translucent, however some transparent specimens have also been reported. They can be vitreous to dull in luster. The crystals generally occur in small sizes, however can make excellent micromounted specimens. Another interesting characteristic of Milarite is some specimens may fluoresce blue-white under short-wave ultraviolet light.

Apart from its type locality of Val Giuf (Val Milar), Tavetsch, Grischum, Switzerland, Milarite has been found at Jaguaracu, Minas Gerais, Brazil; Valencia Mine, Guananajuato, Mexico; Henneberg, Germany; Kola Peninsula, Russia; Mont Saint-Hilaire, Quebec, Canada; Monte Cervandone, Piemonte, Italy; Langesunsfjord, Norway and Maehren, Czech Republic.

Milarite has been cut as a gem, but is rather rare. Its small specimens and its general translucency makes Milarite only really suitable to be cut for collectors of rare gemstones. Good mineral specimens with intense color, nice luster and fluorescence can be very attractive, but mostly under magnification.