Strüverite (variety of Rutile)
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Strüverite is named after Giovanni Strüver (1842-1915), Professor of Mineralogy, University of Rome, Italy.

Discovered in 1907.  IMA status: Not Valid; a variety of Rutile (Discredited by IMA 2006)

Chemistry

Chemical Formula:

(Ti,Ta,Fe²⁺)O₂

Titanium Tantalum Iron Oxide

Molecular Weight:

117.38 gm

Composition:

Tantalum

30.83 %

Ta

37.65 %

Ta₂O₅

Titanium

24.48 %

Ti

40.83 %

TiO₂

Niobium

7.92 %

Nb

11.32 %

Nb₂O₅

Iron

9.52 %

Fe

12.24 %

FeO

Oxygen

27.26 %

O

100.00 %

102.04 %

= TOTAL OXIDE

Classification

Mineral Classification:

Oxides

Dana 8th Edition ID:

4.4.1.3

4 : SIMPLE OXIDES
4 : AX₂

Related to:

Rutile Group. Forms a series with Ilmenorutile; Ta:Nb > 1.

Members of Group:

Rutile Group: Argutite, Cassiterite, Paratellurite, Plattnerite, Pyrolusite, Stishovite, Tripuhyite

Varieties:

None

Synonyms:

Strüverite (of Zambonini)

Crystal Data

Crystallography:

Tetragonal - Ditetragonal Dipyramidal

Crystal Habit:

As Dipyramidal, prismatic crystals, to several cm, with striated prism faces.

Twinning:

Common on {101}

Physical Properties

Cleavage:

Distinct on {110}

Fracture:

Conchoidal

Tenacity:

Brittle

Moh's Hardness:

6.0 - 6.5;  VHN = 911 - 998

Density:

4.20 - 5.80 (g/cm³)

Luminescence:

None

Radioactivity:

Not Radioactive

Optical Properties

Color:

Black; red or reddish brown in transmitted light; light gray in reflected light

Transparency:

Opaque; translucent through thin edges

Luster:

Adamantine, Resinous

Bereflectance:

Weak; R1 - R2: n.d.

Dispersion:

Strong

Pleochroism:

Strong; E = brown; O = dark bluish green or greenish blue

Anisotropism:

Strong

Occurances

Geological Setting:

A late primary mineral in granite pegmatites; rarely detrital.

Common Associations:

Columbite, Ilmenite, Beryl, Cassiterite, Zircon, Monazite, Albite, Microcline

Common Impurities:

Fe, Ta, Nb, Cr, V, Sn

Type Locality:

Craveggia, Val Vigezzo, Peidmont, Italy

Year Discovered:

1907

View mineral photos:

Strüverite Mineral Photos and Locations

More Information

Mindat.org
Webmineral.com

Strüverite is an Iron (Fe), Niobium (Nb) and Tantalum (Ta) bearing variety of Rutile (TiO2) that was named to honor Giovanni Strüver (1842-1915), Professor of Mineralogy, University of Rome, Italy. Strüverite was discredited by the International Mineralogical Association (IMA) in 2006 and determined to be a variety of Rutile and not a distinct mineral species. It was suggested by B. H. Flinter of the Geological Survey Department, Federation of Malaya in 1939 that a proper name for this mineral should be Niobian-Rutile or Tantalian-Rutile due to its Niobium and Tantalum content. Strüverite is closely related to Ilmenorutile. Ilmenorutile has a much high Niobium and much lower Tantalum content than Strüverite. Chemically the two are very similar. However, the specific gravity of Strüverite is around 5.2 compared to 4.3 - 4.6 for Ilmenorutile. Strüverite is typically opaque black with adamantine to resinous luster.

Locations: from Craveggia, Val Vigezzo, Piedmont, Italy. At Vêñá, near Rozná, and Písek, Czech Republic. In the Etta mine, near Keystone, Pennington County, South Dakota, USA. At Tongafeno, Fefana, Mananjary, Ampangabé, and elsewhere in Madagascar. From near Salak North, Kuala Kangsar, Perak, Malaya. At Globe Hill, Western Australia. Other localities are reported, either undefined, or the material requiring modern confirmation.
 

  
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