- Chemistry: TiO2, Titanium Oxide
- Class: Oxides
- Group: Rutile
- Uses: Ore of titanium, pigment and as an ornamental stone when in
Rutile is an interesting, varied and important mineral. Rutile is a
major ore of titanium, a metal used for high tech alloys because of its
light weight, high strength and resistance to corrosion. Rutile is also
unwittingly of major importance to the gemstone markets. It also forms
its own interesting and beautiful mineral specimens.
Microscopic inclusions of rutile in quartz,
and other gemstones,
produces light effects such as cat's eye and asterisms (stars).
A beautiful stone produced by large inclusions of golden rutile needles
in clear quartz is called rutilated quartz. Rutilated quartz is
sometimes used as a semi-precious stone and/or for carvings. This stone
is produced because at high temperatures and pressure, n(SiO2)-n(TiO2)
is in a stable state but as temperatures cool and pressure eases the two
separate with rutile crystals trapped inside the quartz crystals.
is common in rutile crystals, with a cyclic twin forming that is comprised
of six or even eight "twins" arranged in a circle. A Rutile
Star is a formation of crystals of rutile in a six rayed orientation.
The crystals grow off of a hematite crystal and the orientation is caused
by its six rhombic faces.
- Color is black or reddish brown in large thick crystals or golden
yellow or rusty yellow as inclusions or in thin crystals.
- Luster is adamantine to submetallic.
- Transparency: Crystals are transparent in rather thin crystals
- Crystal System is tetragonal; 4/m 2/m 2/m
- Crystal Habits include eight sided prisms and blocky crystals
terminated by a blunt four sided or complex pyramid. The prisms are composed
of two four sided prisms with one of the prisms being dominant. Crystals
with some twins forming hexagonal or octahedral circles. A very common
habit is thin acicular needles (especially as inclusions in other minerals)
or as blades.
- Cleavage is good in two directions forming prisms, poor in a
- Fracture is conchoidal to uneven.
- Hardness is 6 - 6.5
- Specific Gravity is 4.2+ (slightly heavy)
- Streak is brown
- Other Characteristics: Striations lengthwise on crystals, high
refractive index (2.63) gives it a sparkle greater than diamond
- Associated Minerals are quartz,
and other oxides
- Notable Occurrences include Minas Gerias, Brazil; Swiss Alps;
Arkansas, USA and some African locallities.
- Best Field Indicators are crystal habit, streak, hardness, color
and high index of refraction (luster).