Rutile is named after Latin "rutilas" - golden red, alluding to its common colour, especially in transmitted light.
Golden-coloured rutile typically occurs in a slender acicular form. The small needles of rutile found in gems cause an optical phenomenon known as asterism. Asterated gems are known as "star" gems (Star sapphire, Star rubies, etc.).
Rutile has high refractive index and strong dispersion, it gives an adamantine lustre and a diamond-like appearance to its crystals.
Rutile crystals frequently form as elbow or cyclic twins.
|Chemical Formula||Gems, Sixth Edition (2006) , |
|Photos of natural/un-cut material from mindat.org|
|Pale yellow, synthetic rutile may be turned an attractive blue color by heating at over 1000°C in a reducing atmosphere. Heating at 1000°C in oxygen reverses this change (Nassau, 1980) - Nassau (1984)|
|Synthetic rutile: Colourless, yellowish, Transparent; Hardness 6 - 6.5; RI 2.616 - 2.903; Birefringence 0.287; Uniaxial/+; SG 4.26; Inclusions: occasionally gas bubbles - Gemmological Tables, Ulrich Henn and Claudio C. Milisenda, 2004, p 31|
|Physical Properties of Rutile|
|Mohs Hardness||6 to 6.5Blue Chart Gem Identification (2010) , More from other references|
|Specific Gravity||4.20 to 4.30Blue Chart Gem Identification (2010) , More from other references|
|Cleavage Quality||DistinctGemmological Tables (2004) , |
|Fracture||Sub-ConchoidalGemstones (2009) , |
|Optical Properties of Rutile|
|Refractive Index||2.609 to 2.903Blue Chart Gem Identification (2010) , More from other references|
|Optical Character||Uniaxial/+Blue Chart Gem Identification (2010) , More from other references|
|Birefringence||0.287Blue Chart Gem Identification (2010) , More from other references|
|Pleochroism||StrongGemstones (2009) , |
|Dispersion||Very highBlue Chart Gem Identification (2010) , More from other references|
|Chatoyancy||Yes, star 4Blue Chart Gem Identification (2010) , |
|Colour (General)||(Dark) yellowish brown, reddish brown, blackBlue Chart Gem Identification (2010) , More from other references|
|Causes of Colour||Blue (synthetic rutile), Band transition due to the presence of Ti3+Pragmatic Spectroscopy For Gemologists (2011) , |
|Transparency||Transparent,Translucent,OpaqueGemmological Tables (2004) , |
|Lustre||Adamantine,MetallicGems, Sixth Edition (2006) , |
|Fluorescence & other light emissions|
|Fluorescence (General)||InertBlue Chart Gem Identification (2010) , |
|Crystallography of Rutile|
|Crystal System||TetragonalBlue Chart Gem Identification (2010) , More from other references|
|Habit||slender prismatic striated lengthways, variably terminated and often geniculate twinned crystalsGems, Sixth Edition (2006) , |
|Where found:||Rutile occurs as a common high-temperature, highpressure accessory mineral in igneous rocks and granite pegmatites and in regionally metamorphosed rocks including crystalline limestones. Rutile needles are common inclusions in a number of gem minerals.Gems, Sixth Edition (2006) , |
|Mineral information:||Rutile information at mindat.org|
|Significant Gem Localities|