THE MINERAL MILARITE
Milarite is a fairly rare mineral and yet it is one of the two minerals that gives its name to a somewhat large group of silicates, namely the
Milarite - Osumilite Group.
The group is composed of similar cyclosilicate
minerals that are all very rare and very obscure with the exception of milarite,
The primary structural unit of the minerals in the Milarite - Osumilite Group is a most unusual double ring,
Normal rings of cyclosilicates are composed of six silicate tetrahedrons;
The double rings of the Milarite - Osumilite Group minerals are made of two normal rings linked together by sharing one oxygen in each of the tetrahedrons.
The structure is analogous to the dual wheels of a tractor trailer.
Milarite crystals are generally small, but can make excellent micromounted specimens.
They are often colored a muted green or yellow and form good prismatic hexagonal crystals.
Milarite forms as a primary mineral in granitic pegmatites and syenites, hydrothermal veins and alpine clefts.
It has been cut as a gem, but is too rare, small and its general translucency that makes it only suitable to be cut for collectors of rare gemstones.
Milarite is named for its locality of first discovery; Val Giuf (Val Milar), Tavetsch, Grischum, Switzerland.
Milarite has been known as giufite and giuffite, but milarite is the only accepted name now.
Good mineral specimens are available and can be quite attractive, but mostly under magnification.
- Color is colorless, white, pale green or yellow.
- Luster is vitreous to dull.
- Transparency: Crystals are translucent to transparent.
- Crystal System is hexagonal; 6/m 2/m 2/m.
- Crystal Habits include prismatic crystals with a pinacoidal termination.
- Cleavage is poor in one direction.
- Fracture is subconchoidal.
- Hardness is 5.5 - 6
- Specific Gravity is approximately 2.5 - 2.6 (average)
- Streak is white.
- Other Characteristics: Some specimens are fluorescent.
- Notable Occurrences include the type locality of Val Giuf (Val Milar), Tavetsch, Grischum, Switzerland as well as Jaguaracu, Minas Gerais, Brazil; Valencia Mine, Guananajuato,
Mexico; Henneberg, Germany;
Kola Peninsula, Russia;
Quebec, Canada; Monte Cervandone, Piemonte, Italy; Langesunsfjord, Norway and Maehren, Czech Republic.
- Best Field Indicators are hardness, color, luster and locality.