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Titanite (also known as Sphene)

Discovered in 1795; IMA status: Valid (pre-IMA; Grandfathered)

Chemistry

Chemical Formula:

CaTiSiO₅

Calcium Titanium Silicate

Emperical Chemical Formula:

Na_0.97)_∑=8.98V

Molecular Weight:

197.76 gm

Composition:

Calcium

19.25 %

Ca

26.94 %

CaO

La,Ce,Pr,Nd,Sm

3.64 %

RE

4.25 %

REE₂O₃

Titanium

18.16 %

Ti

30.29 %

TiO₂

Aluminum

2.73 %

Al

5.16 %

Al₂O₃

Iron

1.41 %

Fe

2.02 %

Fe₂O₃

Silicon

14.20 %

Si

30.38 %

SiO₂

Oxygen

39.64 %

O

Fluorine

0.96 %

F

0.96 %

F

—

 —  %

F

-O=F₂

100.00 %

99.60 %

= TOTAL OXIDE

Classification

Mineral Classification:

SILICATES (Germanates)

Strunz 8th Ed. ID:

8/B.12-10

Nickel-Strunz 10th Ed. ID:

9.AG.15

9 : SILICATES (Germanates)
A : Nesosilicates
G : Nesosilicates with additional anions; cations in > [6] +- [6] coordination

Related to:

Titanite Group (structurally related to Tilasite Group). Titanite - Malayaite Series. The titanium analogue of Malayaite and Vanadomalayaite. Isostructural with Durangite and Tilasite.

Members of Group:

Titanite Group: Lederite (of Shepard), Malayaite, Natrotitanite, Titanite, Vanadomalayaite 

Varieties:

Chromian Titanite, Eucolite-Titanite, Greenovite, Grothite, Keilhauite, Lederite (of Shepard), Stanniferous Titanite, Yttrian Titanite

Synonyms:

Aspidelite, Castellite, Ligurite, Menakerz, Sphen, Sphene, Titanite (of Klaproth)

Crystal Data

Crystallography:

Monoclinic - Prismatic

Crystal Habit:

Crystals wedge-shaped, flattened or prismatic by extension along [110], to 16 cm; compact, massive

Twinning:

On [100], contact and penetration; less commonly lamellar on [221]

Physical Properties

Cleavage:

Distinct on [110], Imperfect on [100] and [112]; parting due to twinning on [221]

Fracture:

Sub-Conchoidal

Tenacity:

Brittle

Moh's Hardness:

5.0 - 5.5

Density:

3.48 - 3.60 (g/cm³)

Luminescence:

None

Radioactivity:

Mild; GRapi = 3,805.77 (Gamma Ray American Petroleum Institute Units)

Other:

May be metamict.

Optical Properties

Color:

Colorless, Reddish Brown, Red, Yellow, Green, Gray, Black

Transparency:

Transparent to Translucent, Opaque

Luster:

Adamantine to Resinous

Refractive Index:

1.843 - 2.110  Biaxial ( + )

Birefringence:

0.100 - 0.160 (high)

Dispersion:

Extreme; r > v

Pleochroism:

Visible; distinct when deeply colored; X = nearly colorless; Y = yellow to green; Z = red to yellow-orange

Occurances

Geological Setting:

A common accessory mineral in intermediate and felsic plutonic rocks, pegmatites, and alpine veins. In gneisses, schists, and some skarns; rarely detrital.

Common Associations:

Albite, Allanite, Apatite, Biotite, Calcite, Chlorite, Diopside, Epidote, Ilmenite, Magnetite, Monazite, Nepheline

Common Impurities:

Fe, Y, Mn, Al, Ce, Sr, Na, Nb, Ta, Al, Mg, V, F, Zr, Sn

Type Locality:

Titanite occurrence, Hauzenberg, Lower Bavaria, Bavaria, Germany

Year Discovered:

1795

View mineral photos:

Titanite Mineral Photos and Locations

More Information

Mindat.org
Webmineral.com

Sphene (also known as Titanite) is a beautiful gem with high dispersion, high refractive index (greater than Diamond), high birefringence and intense red, green and yellow colors. An intensly vivid green, chromium (Cr) rich variety of Titanite exists called Chromian Titanite. Unfortunately, it also has low hardness and is brittle so not recommenced for jewelry. Sphene is typically slightly to moderately included and clean gems are particularly rare and beautiful.

Sphene is mildly radioactive due to the presence of the Cerium (Ce) and other Rare Earth Elements (REE). Because Sphene is a mildly radioactive mineral it should be stored away from other gems and minerals that are subject to damage from radioactivity and of course human exposure should be limited.

Sphene is often metamict due to the presence of radioactive Cerium (Ce) in its chemical composition. Metamictization is a natural, gradual process of destruction of the internal crystal structure of a mineral due to radiation present in the mineral or from nearby external radiation. Metamictization eventually leaves the mineral amorphous or without any internal crystal structure. Once this process is complete the mineral is described as metamict.

Titanite was named in 1795 by Martin Klaproth for its high titanium content (24%). The name Sphene, a common synonym of Titanite, is from the Greek word sphenos for wedge referring to its characteristic wedge-shaped crystals, was introduced in 1801 by Rene Just Haüy.

Notable occurances of gemmy crystals include Gilget and Badakhshan Provinces, Afghanistan; Pi~no Solo. From Campo do Boa, Capelinha, Minas Gerais, Brazil; Antsiranana and Tuléar Provinces, Madagascar; Skardu District, Baltistan, Northern Areas, Pakistan; and Subpolar Ural Mountains, Russia.

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