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Milarite
Current inventory:  0 gems
 

Chemistry:  K₂Ca₄Al₂Be₄(Si₂₄O₆₀)·(H₂O)
[Hydrated Potassium Calcium Aluminum Beryllium Silicate]

Discovered in 1870;   IMA status: Valid (pre-IMA; Grandfathered).
Milarite was mistakenly named after what was thought to be its locality of discovery; Val Milar, Switzerland. However, Milarite was not discovered there, but instead was first found at Val Giuv, Tujetsch, Grischun, Switzerland. It was later also found at Val Milar.

Classification

Mineral Classification:

Silicates

Strunz 8th Ed. ID:

8/E.22-20

Nickel-Strunz 10th Ed. ID:

9.CM.05

9 : SILICATES (Germanates)
C : Cyclosilicates
M : [Si₆O₁₈]₁₂- 6-membered double rings (sechser-Doppelringe)

Related to:

Milarite - Osumilite Series

Crystal Data

Crystallography:

Hexagonal - Dihexagonal Dipyramidal

Crystal Habit:

Typically as well-formed hexagonal prisms, to 4 cm; as radial-fibrous aggregates and intergrowths.

Twinning:

None

Physical Properties

Cleavage:

[0001] Imperfect, [1120] Imperfect

Fracture:

Conchoidal to Uneven

Tenacity:

Brittle

Hardness (Mohs):

5.5 - 6.0

Density:

2.46 - 2.61 (g/cm³)

Luminescence:

Some specimens may be fluorescent

Radioactivity:

Barely Detectable; GRapi = 56.71 (Gamma Ray American Petroleum Institute Units)

Optical Properties

Color:

Colorless, White, Greenish White, Yellowish White

Transparency:

Transparent to Translucent, Opaque

Luster:

Vitreous

Refractive Index:

1.532 - 1.548  Uniaxial ( - ); anomalously Biaxial, sectored, with a Uniaxial core

Birefringence:

0.0030 - 0.0160

Dispersion:

n/a

Pleochroism:

n/a

Occurances

Geological Setting:

In alpine and low-temperature hydrothermal veins; in aplites, syenites, and granite pegmatites.

Common Associations:

Albite, Bavenite, Bertrandite, Beryl, Calcite, Chlorite, Fluorite, Minasgeraisite-(Y), Muscovite, Orthoclase, Phenakite, Quartz

Common Impurities:

Sodium (Na)

Type Locality:

Giuv Valley, Tujetsch (Tavetsch), Vorderrhein Valley, Grischun (Grisons; Graubünden), Switzerland

Year Discovered:

1870

View mineral photos:

Milarite Mineral Photos and Locations

More Information

Mindat.org
Webmineral.com

Milarite is a very rare gem. Crystals are colorless, pale green, yellowish green and yellowish. Most crystals are not facetable but occassional very small gemmy crystals are found. There are very few sources for Milarite crystals. These include St. Gotthard, Switzerland; Minas Gerais, Southeast Region, Brazil; Guanajuato, Mexico; Fujian Province, China; Arandis, Swakopmund District, Erongo Region, Namibia and Albany, Carrol County, New Hampshire, USA. 
 

  
Milarite gems for sale:

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