ClassicGems.net

Wiluite

Discovered in 1793; IMA status: Valid (IMA approved 1998)

Chemistry

Chemical Formula:

Ca₁₉(Al,Mg,Fe,Ti)₁₃(B,Al,[ ])₅Si₁₈O₆₈(O,OH)₁₀

Calcium Aluminum Magnesium Iron Titanium Boron Silicate Hydroxide

Molecular Weight:

2,924.83 gm

Composition:

Calcium

26.04 %

Ca

36.43 %

CaO

Magnesium

3.99 %

Mg

6.61 %

MgO

Titanium

0.82 %

Ti

1.37 %

TiO₂

Aluminum

6.46 %

Al

12.20 %

Al₂O₃

Iron

1.72 %

Fe

2.46 %

Fe₂O₃

Silicon

17.28 %

Si

36.98 %

SiO₂

Boron

0.96 %

B

3.09 %

B₂O₃

Hydrogen

0.07 %

H

0.62 %

H₂O

Oxygen

42.67 %

O

100.00 %

100.00 %

= TOTAL OXIDE

Classification

Mineral Classification:

Silicates (Germanates)

Strunz 8th Ed. ID:

8/C.26-20

Nickel-Strunz 10th Ed. ID:

9.BG.35

9 : SILICATES (Germanates)
B : Sorosilicates
G : Sorosilicates with mixed SiO₄ and Si₂O₇ groups; cations in octahedral [6] and greater coordination

Related to:

Vesuvianite Group

Varieties:

n/a

Synonyms:

IMA1997-026

Crystal Data

Crystallography:

Tetragonal - Ditetragonal Dipyramidal

Crystal Habit:

Euhedral Crystals; occurs as well-formed crystals showing good external form.

Twinning:

None

Physical Properties

Cleavage:

{100} Poor

Fracture:

Irregular/Uneven

Tenacity:

Brittle

Moh's Hardness:

6.0

Density:

3.36 (g/cm³)

Luminescence:

None

Radioactivity:

Not Radioactive

Optical Properties

Color:

Dark Green

Transparency:

Translucent to Opaque

Luster:

Vitreous

Refractive Index:

1.721 - 1.725  Uniaxia ( + )

Birefringence:

0.004

Dispersion:

Very high

Pleochroism:

Very Strong

Occurances

Geological Setting:

A low-temperature, Si-deficient variety of vesuvianite occurs in porous tetrahedral "achtarandite” pseudomorphs consisting of hibschite, along the banks of the Wiluy River, Yakutia, Russia, the type locality.

Common Associations:

Wollastonite and olive-green Grossulars.

Common Impurities:

n/a

Type Locality:

Wilui River Basin, Saha Republic, Eastern-Siberian Region, Russia

Year Discovered:

1793; IMA approved 1998

View mineral photos:

Wiluite Mineral Photos and Locations

More Information

Mindat.org
Webmineral.com

Wiluite is a rare and complex boron (B) bearing silicate mineral that is a member of the Vesuvianite mineral group that includes Cyprine, Vesuvianite and Wiluite. Wiluite is, esentially, Vesuvianite with boron (B) added to its chemistry. The incorporation of boron into the Vesuvianite chemistry leads to changes in the crystal-chemical features, as well as in physical and chemical properties including the inversion of the optical sign from (–) for Vesuvianite to (+) for Wiluite. Wiluite crystals are usually well-formed euhedrals of dark green, brownish or black colors and are translucent to opaque.

Wiluite was discovered in 1793 and named in 1802 by Basil Severgin after the discovery locality in the Wilui River Basin, Saha Republic, Eastern-Siberian Region, Russia. The mineral discovered was originally thought to be a variety of Vesuvianite. The first description of the crystal structure of this “Vesuvianite” from the Wilui River Basin was provided by Warren and Modell in 1931. Wiluite was not approved as a distinct mineral species by the IMA until 1998.

Because of its exceptional structural and chemical complexity, Wiluite has attracted the attention of geologists, chemists, petrologists and mineralogists for more than two hundred years: Pallas in 1793; Klaproth in 1797; Jannasch in 1884; Prendel in 1887; Widman in 1890; Jannasch and Weingarten in 1896; Wherry and Chapin in 1908; Kurbatov in 1946; Lyachovich in 1954; Groat in 1992, 1994, 1996, 1998, 2000 and 2013; Galuskina in 1998; Galuskin and Galuskina in 2000; Galuskin in 2005; and Bellatreccia in 2005 [*].

Wiluite is only known from two locations, the type locality at the Vilyui River Basin (Vilui River Basin; Wilui River Basin), Saha Republic (Sakha Republic; Yakutia), Eastern-Siberian Region, Russia; and a very minor source at Ariccia, Latium, Italy.

Wiluite gems for sale:

We have not photographed our Wiluite gems. Please check back soon.