Sapphire

Big Photo

Sri Lanka
1.14 carats
© Mineral Classics

The name Sapphire derives from Greek "sappheiros" - blue. In antiquity, any blue stone such as lazurite, was called Sapphire.

At first only the blue variety was called Sapphire. Today corundums of gemstone quality of all colours except red are called Sapphire. The most desired colour is a pure cornflower-blue. Some blue and grayish-blue Sapphires (Sri Lanka, Thailand, Tanzania, Colombia, and others) exhibit a reddish or violet-red tint under artificial light - the alexandrite effect which is caused by admixtures of chromium and vanadium, the intensity is related to the concentration of these elements.

Inclusions of rutile needles cause a silky shine; aligned needles cause a six-rayed star sapphire.

Sapphires are commonly worn in jewelry. Because of remarkable hardness (9 in Mohs Scale), Sapphires are used in some non-ornamental applications (scientific instruments, high-durability windows, etc.)

Sapphire Gemstones by Colour

This table shows the variety of hues this gemstone can be found in. Click on a photo for more information.
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 

Sapphire Gemstones by Size

This table shows distribution of Sapphire gemstone sizes that are listed on this site. This can give a good indication as to the general availability of this gemstone in different sizes.
Contributed photos
Lightest:0.09 cts
Heaviest:563.35 cts
Average:6.09 cts
Total photos:239
Do you have a larger Sapphire? Why not upload a photo?
Significant stones
Black Star of Queensland, Star Sapphire733 cts
0.09ct to 56.42ct56.42ct to 112.74ct112.74ct to 169.07ct169.07ct to 225.39ct225.39ct to 281.72ct281.72ct to 338.05ct338.05ct to 394.37ct394.37ct to 450.70ct450.70ct to 507.02ct507.02ct to 563.35ct
General Information
A variety or type of:Corundum
Varieties/Types:
Padparadscha - A salmon-pink coloured Sapphire.
Star Sapphire - A chatoyant sapphire showing asterism.
Chemical Formula
Al
 
2
O
 
3
Michael O’Donoghue, Gems, Sixth Edition (2006)
Significant stones
ImageNameWeightCountry of OriginCurrent Owner
Black Star of Queensland, Star Sapphire733.00 ctsAustraliaSmithsonian Institute
Star of India563.35 ctsSri Lanka
Logan sapphire422.99 ctsSri Lanka
Star of Asia330.00 ctsMyanmar
Pride of Queensland169.00 ctsAustralia
Ceylon151.00 ctsSri Lanka
Midnight Star116.75 ctsSri Lanka
Stewart (Stuart) Sapphire104.00 ctsBritish Crown
Click here to view all significant Sapphire gemstones
Photos of natural/un-cut material from mindat.org
Sapphire Treatments
Star-diffusion(titanium): Surface-diffusion on a gem already cut into cabochon shape: strong star effect occuring at and just below the surface. Fiber-optic light: shallow fuzzy whitish surface layer. Very fine "silk", thin fabric structure. In most cases, unlike natural, the rays do not show a 90° orientation to color zoning (crystal faces).

Diffusion (beryllium): Most corundum with orangy hue, strong bi-coloration and saturated colours, typically yellow, orange, red-orangy, orangy-pink, pink-purple, hot pink, and padparadscha colour are beryllium treated. Other colours may also result or be improved by this treatment (typically ruby, blue and green sapphires): standard tests are limited especially for clean light gems. Very high heat treatment is required to diffuse the colouring agent into the gem. Resulting inclusions are distorted melted guest crystals such as white formless zircon (often with gas bubble). Most melted crystals are surrounded by discoid fractures often with dendritic pattern (partial recrystallization); they often show a cottony appearence. Dot-like inclusions are common. Colour concentration may be seen arround melted guest crystal. Colour zone following the shape of the gem (rim with distinct coloration from core): immersion in methylen iodide (or coconut/baby oil), diffused transmitted light, frosted complementary colour filters (blue for yellow-orangy).

YELLOW - Heat-treated: darken temporarily if heated (spoon and lighter 2 min or 15 min within 1 cm of 150W spot light). Yellow-orangy once produced by irradiation: colour fading permanently if heated.

Diffusion: colourless to yellow-orangy rim, blue haloes/spots (internal diffusion). Synthetic overgrowth can often be seen at girdle and culet: roiled appearance in transmitted light, light areas between cross-polarizing filters.

BLUE – Heat-treated: dot-like partially dissolved “silk”, rounded melted crystals surrounded by discoid fractures, diffused colour banding, blue spots.

GRAYISH-BLUE and WHITISH to WHITE, semitransparent sapphires with silky lustre due to rutile microinclusions, called "geuda" in Sri Lanka, become transparent and acquire a beautiful, bright blue colour after calcination at temperatures of 1600°C and higher. This is caused by the resorption of rutile and transfer of Ti4+ ion into the crystal lattice of corundum. This Ti4+, in combination with Fe2+, produces a colour centre. The intensity of the acquired colour is related to the ratio of iron and titanium admixtures in the initial raw material. Increased iron content results in an excessively dark colour (Harder, 1992).

Some COLOURLESS and PALE YELLOW iron-bearing sapphires (Sri Lanka and others) become bright yellow after annealing in oxidizing conditions due to an increase in the number of chromophore centres Fe3+ and Fe3++Fe3+.

Surface diffusion: looking table down with diffused transmitted light (immersion): colour concentration at facet junctions, in cracks, around girdle (cabs), uneven facet to facet colour distribution. May show natural colour zoning.

THERMAL DIFFUSION method is more universal and is suitable for treatment of pale-coloured sapphires, which are depleted in iron or do not contain oriented inclusions. In these cases the cut sapphires are exposed to a long (one day and more) exposure to temperatures of 1800 to 1900°C in a powder of titanium and iron oxides. Chromium oxide is used to produce pink and red colours, strontium for orange, cobalt for bright blue, etc. The diffusion of chromophore elements produces colour in a thin superficial layer of sapphire to a depth of tenths of a millimeter (Hanni, 1982).

In the 1980s the world market was saturated with annealed light blue and blue sapphires, which caused problems in distinguishing them from rare and more expensive stones with natural colour. "Fire marks", the discoid cracks of internal tension, are easily observed at medium magnification; the complete disappearance of CO2 inclusions; melted surfaces of large solid inclusions; the occurence of a network of small, thin channels; the sharp contrast between coloured and almost colourless zones; the decrease of dichroism, etc. are evidence of thermal processing. - E.Ya.Kievlenko, Geology of gems, 2003, p. 41
Sapphire Simulants
Some imitations are made from doublets-blue cobalt glass with a crown of garnet or a crown of green sapphire and a pavillion of synthetic blue sapphire. Lately doublets have appeared using 2 small natural sapphires. - Gemstones of the world, Walter Schumann, 2001, p 86
Physical Properties of Sapphire
Mohs Hardness9
Herve Nicolas Lazzarelli, Blue Chart Gem Identification (2010)
More from other references
Specific Gravity3.95 to 4.03
Walter Schumann, Gemstones of the world (2001)
More from other references
TenacityBrittle
Michael O’Donoghue, Gems, Sixth Edition (2006)
Cleavage QualityNone
Michael O’Donoghue, Gems, Sixth Edition (2006)
FractureUneven,Conchoidal
Michael O’Donoghue, Gems, Sixth Edition (2006)
Optical Properties of Sapphire
Refractive Index1.762 to 1.788
Walter Schumann, Gemstones of the world (2001)
More from other references
Optical CharacterUniaxial/-
Herve Nicolas Lazzarelli, Blue Chart Gem Identification (2010)
More from other references
Birefringence0.008 to 0.009
Herve Nicolas Lazzarelli, Blue Chart Gem Identification (2010)
More from other references
PleochroismPink sapphires - strong: pink - pinkish-red; Orange/brown stones - distinct: brownish-orange - orangy to colorless; Yellow sapphires - weak: light yellow - yellow-(orangy); Violet/purple sapphires - distinct: bluish-purple - yellow-brown/orange; Blue sapphires - strong: dark (violetish) blue - greenish-blue; Green sapphires - distinct: yellow-green - green to blue-green
Herve Nicolas Lazzarelli, Blue Chart Gem Identification (2010)
More from other references
Dispersion0.018
Michael O’Donoghue, Gems, Sixth Edition (2006)
ChatoyancyStar 6 - (rare)12
Herve Nicolas Lazzarelli, Blue Chart Gem Identification (2010)
Colour
Colour (General)Blue in various tones, colorless, pink, orange, yellow, green, purple, black
Walter Schumann, Gemstones of the world (2001)
More from other references
Colour (Incandescent Light)In artificial incandescent light, some sapphires can appear to be ink-colored or black-blue.
Walter Schumann, Gemstones of the world (2001)
Colour (Chelsea Filter)Green synthetic: usually red. Pink: reddish.
Herve Nicolas Lazzarelli, Blue Chart Gem Identification (2010)
Causes of ColourThe coloring agents in blue sapphire are iron and titanium; and in violet stones, vanadium. A small iron content results in yellow and green tones; chromium produces pink, iron, and vanadium orange tones.
Walter Schumann, Gemstones of the world (2001)
TransparencyTransparent,Translucent,Opaque
Walter Schumann, Gemstones of the world (2001)
LustreSubadamantine,Vitreous,Pearly
Michael O’Donoghue, Gems, Sixth Edition (2006) Pearly on parting surfaces
Fluorescence & other light emissions
Fluorescence (General)Green synthetic: commonly orange to dark red. Yellow/orange: inert to strong orange. Pink: inert to orangy-red; synthetic: commonly strong orangy-red.
Herve Nicolas Lazzarelli, Blue Chart Gem Identification (2010)
Fluorescence (Short Wave UV)Colorless: mostly inert, sometimes dark red-(orangy), synthetic: common (chalky) blue. Green: inert to weak orangy-red. Yellow/orange synthetic: (very) weak yellowish-orange to pinkish-red. Blue: weaker if any; Synthetic: mostly chalky blue-(green). Heat-treated blue: the colorless portions of the gem may fluoresce chalky blue-(green)
Herve Nicolas Lazzarelli, Blue Chart Gem Identification (2010)
Fluorescence (Long-Wave UV)Colorless: inert to orangy-red; colorless synthetic: inert. Green: inert. Yellow/orange synthetic: strong yellowish to reddish orange. Blue: inert to orangy-red.
Herve Nicolas Lazzarelli, Blue Chart Gem Identification (2010)
Crystallography of Sapphire
Crystal SystemTrigonal
Herve Nicolas Lazzarelli, Blue Chart Gem Identification (2010)
HabitDoubly pointy, barrel-shaped, hexagonal pyramids, tabloid-shaped
Walter Schumann, Gemstones of the world (2001)
More from other references
Geological Environment
Where found:Host rocks of sapphire are dolomotized limestones, marble, basalt, or pegmatite. It is mined mainly from alluvial deposits or deposits formed by weathering, rarely from the primary rock.
Walter Schumann, Gemstones of the world (2001)
Spectrographic Data
Calculated Spectra:
Click spectra for more information
Sapphire - Locality: Unknown
Sapphire - Locality: Afghanistan
Sapphire - Locality: Kenya
Sapphire - Locality: Mozambique
Sapphire - Locality: Tunduru, Tanzania
Sapphire - Locality: Unknown (possibly Australia)
Sapphire - Locality: Unknown
Inclusions in Sapphire
Partially healed fractures ("fingerprint", "fly's wing"), rutile needles ("silk") intersecting at 60°-120° and other guest crystals. For pink stone: cluster of transparent rounded or angular crystals (zircon) - Blue Chart Gem Identification, Herve Nicolas Lazzarelli, 2010, p. 2
Further Information
Mineral information:Sapphire information at mindat.org
Copyright © Jolyon & Katya Ralph 1993-2017. Site Map. Locality, gem & photograph data are the copyright of the individuals who submitted them. For more information please contact the . Gemdat.org is an online information resource dedicated to providing free gemmological information to all.