Ruby is the red variety of corundum. It is one of the most highly prized gemstones and the finest stones command the highest prices per carat at auction. The name is derived from the Latin word ruber (red). It was called ratnaraj, meaning the "King of Gems" by ancient Hindus. The line between ruby and pink sapphire is not clearly defined and can be quite subjective. It is the birthstone for July. Around 1910 the first synthetic ruby was available in the marketplace. Flame-fusion lab created ruby may be cut from boules weighing in excess of 400 carats.
General Information
- Classification
- Optical Properties
- Characteristic Physical Properties
- Chemistry & Crystallography
Common Name
Ruby
Species
Corundum
Transparency
Transparent - Opaque
Dispersion
Strength: Moderate Fire Value: 0.018
Refractive Index
1.762-1.770
Tolerance:(+0.009/-0.005)
Birefringence
0.008-0.01
Optic Character
Uniaxial
Optic Sign
Negative
Polariscope Reaction
Doubly Refractive (DR)
Fluorescence
SWUV: Weak to strong red
LWUV: Weak to moderate red
CCF Reaction
Red glow
Pleochroism
Dichroic, moderate to strong orangy red and purplish red
Hardness
9
Streak
White
Specific Gravity
3.950-4.100 Typical:4.000
Toughness
Excellent
Inclusions
This stone has type II clarity. Sometimes rubies have silk, rutile, boehmite, apatite, calcite or zircon crystals, fingerprint and negative crystal inclusions. Some stones show hexagonal growth and color zoning. Untreated stones will usually have inclusions intact. Heat treated stones will have fracture halos, discoid fractures or snowballs around crystal inclusions (untreated stones from magmatic areas might also show these characteristics). Silk will be broken and might show sintered areas especially around the girdle.
Luster
Bright Vitreous
Stability
Excellent
Fracture
Conchoidal, Uneven
Cleavage
None
Chemical Name
aluminum oxide
Chemical Formula
Al2O3
Crystal System
Trigonal
Chemistry Classification
Oxide
Ruby Colors
-
Red
-
Red
-
Red
Ruby Spectra
RUBY - BURMA UNTREATED (ε ray)
Broad central absorption has narrowed. The two lines at 668nm. and 659nm. are seen as fluorescent lines. Fluorescence in fine specimens can be as strong as that seen in lab created rubies.
RUBY - VERNEUIL lab created. (Unpolarized
Color due to chromium. Controlled supply of chromium oxide in the production of modern lab created ruby can result in a more intense, slightly purplish red stone. The resulting spectrum shows an intense dark absorption band centered at 550nm. together with the usual features of the lines in the blue and the fluorescing doublet in the deep red. The violet is totally absorbed
RUBY - VERNEUIL Lab Created (Unpolarized
Color due to chromium. The absorption spectra is essentially the same for that of natural ruby. Fine lines in blue plus lines in the red. Near the left side of the red, the thick line may appear as double. The line may even glow as an emission line, particularly if the stone is being viewed in reflected light
RUBY - VERNEUIL lab created. (Fluorescence spectrum
An intense light source placed close to the stone and scattered from within it, can enter the spectroscope slit indirectly. In this way a subdued spectrum is seen in which any fluorescence lines stand out against a dark background. In the modern chromium rich, iron free, lab created ruby a spectacular group of fluorescing lines may be seen, dominated by the intense doublet at 693/693nm
RUBY - VERNEUIL Lab created (Fluorescence spectrum
When the lighting is suitably adjusted the doublet at 693/694nm. can be seen as a dark absorption line. If only the o-ray ray is observed this doublet will be seen at its strongest together with finer lines at 668nm. and 659nm. The Broad absorption now extends from 610nm. to 495nm. leaving a narrower window in which the absorption lines at 468nm. and 475/476nm. appear more intense, after which total absorption follows
RUBY - VERNEUIL lab created. (ω ray)
This gem usually shows an intense dark absorption band centered at 550nm. together with the usual features of the lines in the blue and the fluorescing doublet in the deep red. The violet is totally absorbed.
RUBY - VERNEUIL Lab Created (ω ray)
Color due to chromium. The absorption spectra is essentially the same for that of natural ruby. Fine lines in blue plus lines in the red. Near the left side of the red, the thick line may appear as double. The line may even glow as an emission line, particularly if the stone is being viewed in reflected light. The stronger and more purplish pink color of the o-ray causes the central absorption band to broaden. The doublet in the red is seen to be fluorescing fairly strongly which is characteristic of the o-ray. The lines in the blue are prominent and the violet totally absorbed
RUBY - VERNEUIL lab created. (ε ray)
This gem usually shows an intense dark absorption band centered at 550nm. together with the usual features of the lines in the blue and the fluorescing doublet in the deep red. The violet is totally absorbed. As we rotate the polarizing filter and isolate the e-ray variations occur in the spectrum. The doublet in the red is less intense and the fine line in the red at 595nm. is present but the one at 668nm. seen in the o-ray is now absent. The main absorption band has become narrower and the blue area has widened considerably to show the lines clearly before total absorption takes over
RUBY - VERNEUIL Lab Created (ε ray)
The absorption spectra is essentially the same for that of natural ruby. Fine lines in blue plus lines in the red. Near the left side of the red, the thick line may appear as double. The line may even glow as an emission line, particularly if the stone is being viewed in reflected light. In this instance the color produced by the e-ray is more of an orange pink, as a result of which the intensity and width of the central absorption band is considerably diminished. This allows more transmission of orange and green light in this direction. The fluorescence of the doublet in the red is weaker but the lines in the blue are still prominent before total absorption takes over in the violet.
RUBY - THAI UNTREATED (Unpolarized)
Color due to chromium. The spectrum of this rather dark purplish red ruby shows the typical broad absorption band in the green area and the fluorescing doublet at 694/693nm. in the red associated with chromium. However, due to the high iron content the fluorescing doublet is weak and the lines in the blue rather vague
RUBY - THAI UNTREATED (Fluorescence spectrum)
The iron content has weakened the fluorescence considerably and any attempt to capture this in scattered light is poor
RUBY - THAI UNTREATED (ω ray
The spectrum typically shows a broad absorption band in the green area and the fluorescing doublet at 694/693nm. in the red associated with chromium. When the o-ray is polarized via the pavilion facets the central absorption band broadens and the doublet in the red fluoresces more strongly. However, absorption in the deep blue-violet area increases, making it more difficult to resolve the lines in the narrow blue window. This could be because of further absorption in this area due to the iron content.
RUBY - THAI UNTREATED (ε ray)
The spectrum typical shows a broad absorption band in the green area and the fluorescing doublet at 694/693nm. in the red associated with chromium. However, due to the high iron content the fluorescing doublet is weak and the lines in the blue rather vague. The most noticeable difference in the e-ray is the considerably narrower center absorption band. The fluorescing doublet is again much weaker and although transmission in the green-blue area has increased, the narrow lines are still difficult to see due to the greater absorption in the deep blue.
RUBY - KASHAN Lab Created (Unpolarized)
The typical chromium spectrum of a broad band centered at 550nm.in the green and the lines in the blue at 476/475nm and 468nm. are present. However, the doublet in the red at 694/693nm. is constantly seen as an emission line, rather than appearing as dark absorption lines
RUBY - KASHAN Lab Created (Fluorescence spectrum)
In scattered lighting conditions the doublet in the deep red is seen as a strongly fluorescing emission line, and occasionally the two lines at 668nm. And 659nm. may also be seen to fluoresce, even if they are not easily detected as absorption lines in transmitted light
RUBY - KASHAN Lab Created (ω ray)
The typical chromium spectrum of a broad band centered at 550nm.in the green and the lines in the blue at 476/475nm and 468nm. are present. However, the doublet in the red at 694/693nm. is constantly seen as an emission line, rather than appearing as dark absorption lines. A slight increase in the width of the central absorption band. The doublet in the red continues to fluoresce and the lines in the blue are still present.
RUBY - KASHAN Lab Created (ε ray)
The typical chromium spectrum of a broad band centered at 550nm.in the green and the lines in the blue at 476/475nm and 468nm. are present. However, the doublet in the red at 694/693nm. is constantly seen as an emission line, rather than appearing as dark absorption lines. Rotating the polarizing filter 90 degrees produces a narrower and less intense absorption in the green area which allows more transmission of orange light. The other lines are also weaker.
RUBY - BURMA UNTREATED (Unpolarized)
Color due to Chromium Fluorescence of the strong doublet at 694/693nm. A broad absorption band centered at 550nm. Violet is absorbed and lines are seen in the remaining blue window at 476/475nm. and 468nm. Other fine lines normally seen in the red have been masked by the intense transmission in this area.
RUBY - BURMA UNTREATED (Fluorescence spectrum)
Light scattering can be induced by manipulation of the light source to an extent that mainly the red area of the spectrum is transmitted. As a result, any fluorescence is intensified and becomes more visible. In this way the two lines at 668nm. and 659nm. are seen as fluorescent lines, together with the intense doublet at 694/693nm.
RUBY - BURMA UNTREATED (ω ray)
Color due to chromium. Strong fluorescence of the strong doublet at 694/693nm. A slightly broader absorption band centered at 550nm. Violet is absorbed and lines are seen in the remaining blue window at 476/475nm. and 468nm. Other fine lines normally seen in the red have been masked by the intense transmission in this area.
We acknowledge the significant scientific contributions of John S Harris, FGA to the study of gemstone spectra and with deep appreciation to him, acknowledges the use of his images and related notes about gemstones and their spectra in the educational materials on this website.
Alternate Names
Mahaleo Ruby
Countries of Origin
Tanzania, United Republic Of; Myanmar; Afghanistan; Russian Federation; Viet Nam; Czechia; Guinea; United States of America; Madagascar; Thailand; Sweden; Mozambique; Pakistan; Morocco; Unknown; China; Brazil; Nigeria; Argentina; Sri Lanka; Zambia; Kenya; Switzerland; India; Norway; Namibia; South Africa; Ethiopia; Greenland; Tajikistan; Indonesia
History
Rubies. We desire them. Their rich reds are powerful, seductive, and inflaming. Ruby has been a treasure for centuries - the ancient Hindus named it the King of Gems. In fact, the Sanskrit word for ruby is ratnaraj, which means, "the King of Gems." Ruby is considered the gemstone of passion and of lovers; it's the quintessential symbol for red. Fine rubies are among the most costly and valuable gems of the corundum family, which includes sapphires in all colors (except red). Ruby is a 9 on the scale of hardness, so it's a fabulous choice for a wear-every-day, signature gemstone. It's red color works with white, rose, or yellow metals, which means you have plenty of options in jewelry. July babies, this is your birthstone. But move over - there are plenty of us who wear rubies for the sheer beauty of them!
Care
Untreated and heated rubies just need normal care. Avoid recutting or chipping coated or surface diffused stones. Avoid common household chemicals, steam cleaners, ultrasonic cleaners and a jeweler’s torch with lead glass filled, dyed or oiled/resin filled stones.
More About Ruby
Rubies rank among the four gemstones once called precious: diamond, emerald, ruby and sapphire. Their red color has put them in the forefront of folklore for centuries. The early Burmese thought ruby would impart invulnerability to the wearer, which made it a must in battle. In the middle ages, it was believed that ruby had an inner fire that could not be extinguished. And in the 16th century it was written that ruby had magical powers and could, "preserve health, remove evil thoughts, reconcile disputes and control amorous desires"... among other things. Choose your ruby, get it home, wear it and enjoy it. You'll see why we at JTV® revere it.
Creation Method
Lab Created Czochralski
Synthetic ruby can be created in many ways, one of which is called the Czochralski method. During this process, the various elements that make up ruby are melted in a platinum crucible. A small gem crystal (called a seed) attached to a rod is then dipped into the melt and slowly pulled away as the crystal grows around the seed. For this reason, the Czochralski method is also known as crystal pulling. Synthetic gems have the same chemical, optical, and physical properties of their natural counterparts, but are a more cost-effective alternative to a natural gem.
Lab Created Czochralski Ruby
- Classification
- Optical Properties
- Characteristic Physical properties
Common Name
Lab Created Czochralski
CCF Reaction
red
Specific Gravity
3.950
Toughness
Excellent
Inclusions
Stones are almost always inclusion free. If internal characteristics are present they are gas bubbles, curved striae that is hard to see and smoke-like swirling veil-like inclusions.
Stability
Excellent
Lab Created Hydrothermal
Hydrothermally grown synthetic rubies crystallize slowly out of a solution (a mix of water and dissolved elements) that has been exposed to heat and pressure similar to the conditions on Earth under which the natural gem mineral grows. Synthetic gems have the same chemical, optical, and physical properties of their natural counterparts, but are a more cost-effective alternative to a natural gem.
Lab Created Hydrothermal Ruby
- Classification
- Optical Properties
- Characteristic Physical properties
Common Name
Lab Created Hydrothermal
CCF Reaction
red
Specific Gravity
3.950
Toughness
Excellent
Inclusions
Look for chevron, wavy, zig-zag or mosaic growth patterns in hydrothermal synthetic ruby because stones might show growth zoning similar to natural ruby. Fingerprint like inclusions with 2-phase and 3-phase inclusions can be seen in stones. Sometimes flake like copper inclusions are visible in reflected light.
Stability
Excellent
Lab Created Flux
One method of creating synthetic ruby is called flux growth. During the flux growth process, flux, a substance that reduces the melting point of surrounding material, is combined, in a metal-lined crucible, with the elements that make up a specific gem mineral. The crucible is heated until its contents are liquid and then it is allowed to cool very slowly. As cooling continues, the gem mineral crystallizes from the solution. Flux grown synthetic gems can take up to a year to grow to a facetable size, but the exceptional clarity of these gems is well worth the wait! Synthetic gems have the same chemical, optical, and physical properties of their natural counterparts, but are a more cost-effective alternative to a natural gem.
Lab Created Flux Ruby
- Classification
- Optical Properties
- Characteristic Physical properties
Common Name
Lab Created Flux
CCF Reaction
red
Specific Gravity
3.950
Toughness
Excellent
Inclusions
Platinum platelets from the crucible that appear metallic in reflected light but appear dark when stone is lit from behind. Flux is often white, brownish, yellow or orange but can be colorless. Flux inclusions can appear like natural fingerprint inclusions, wispy veils, comet tails, coarse globules of flux that can have a myriad of appearances from drippy, tubular or rod like or icicle looking, to clouds and minute particles, Stone might display angular growth zoning similar to natural.
Stability
Very Good
Lab Created Flame Fusion
The flame fusion process for creating gems, also called the Verneuil process, is the most affordable and common synthesis method for producing corundum (ruby and sapphire) and spinel. Powdered chemicals (the building blocks of the gem) are dropped through a high-temperature flame. The molten powder repeatedly falls from the flame onto a rotating pedestal, creating a synthetic crystal, called a boule, which can later be faceted into a gemstone. Synthetic gems have the same chemical, optical, and physical properties of their natural counterparts, but are a more cost-effective alternative to a natural gem.
Lab Created Flame Fusion Ruby
- Classification
- Optical Properties
- Characteristic Physical properties
Common Name
Lab Created Flame Fusion
CCF Reaction
red
Specific Gravity
3.950
Toughness
Excellent
Inclusions
Stones may display face up pleochroism, curved striae that crosses facet junctions and strings of gas bubbles that might be mistaken for needles. It might be possible to see Plato lines or twinning planes under magnification and immersion with polarized light. Sometimes heated with borax to created fingerprint like inclusions to mask curved striae.
Stability
Excellent
Lab Created Floating Zone
One method of creating synthetic ruby is called floating zone. In this method of gem synthesis, originally developed by engineers to create super pure silicon, a sintered rod of powdered material, comprised of elements necessary for the gem to grow, is heated with infrared radiation in a vacuum while the ends of the rod are rotated in opposite directions. Since all impurities including air are removed during crystallization, very clean crystals can form.
- Classification
- Optical Properties
- Characteristic Physical properties
Common Name
Lab Created Floating Zone
CCF Reaction
red
Specific Gravity
3.950
Toughness
Excellent
Inclusions
Stones are almost always inclusion free. If internal characteristics are present they are gas bubbles that are not perfectly round and swirls of color.
Stability
Excellent
Optical Phenomena
Star
Star rubies will have silk or sets of parallel rutile needles that produce a 6-ray star, hexagonal growth lines, color zoning and mineral inclusions. Weak and less well-formed stars along with weaker body color is typical of natural stones. In natural stones at least one ray of the start will be perpendicular to the hexagonal growth zones.
Star Ruby
- Classification
- Characteristic Physical properties
Common Name
Star
Specific Gravity
3.950
Toughness
Good
Stability
Good
Cat's Eye
The term cat's eye, or chatoyancy, is used to describe a phenomenal optical property in gemstones, in this case ruby. The effect, when present, appears as a bright, narrow slit similar to the pupils in the eyes of your favorite feline. This phenomenon is caused by parallel fibrous or needle-like inclusions that interfere with the passage of light through the crystal, scattering and reflecting light back to the viewer as a thin line.
- Classification
- Characteristic Physical properties
Common Name
Cat's Eye
Specific Gravity
3.950
Toughness
Good
Inclusions
Cat's-eye rubies will have silk or sets of parallel rutile needles, hexagonal growth lines, color zoning, liquid, negative and mineral inclusions. Some stone might show twinning.
Stability
Good
Lab Created Flame Fusion Star
Synthetic star ruby exhibits the optical phenomenon called asterism, a star-like pattern created on the surface of a gemstone when light encounters parallel fibrous, or needle-like, inclusions within its crystal structure. Light that strikes the inclusions within the gem reflects off of the inclusions, creating a narrow band of light. When two or more intersecting bands appear, a star pattern is formed. The flame fusion process for creating gems, also called the Verneuil process, is the most affordable and common synthesis method for producing corundum (ruby and sapphire) and spinel. Powdered chemicals (the building blocks of the gem) are dropped through a high-temperature flame. The molten powder repeatedly falls from the flame onto a rotating pedestal, creating a synthetic crystal, called a boule, which can later be faceted into a gemstone. Synthetic gems have the same chemical, optical, and physical properties of their natural counterparts, but are a more cost-effective alternative to a natural gem.
Lab Created Flame Fusion Star Ruby
- Classification
- Characteristic Physical properties
Common Name
Lab Created Flame Fusion Star
Specific Gravity
3.950
Toughness
Good
Inclusions
Flame fusion stones might display curved growth and a unusually display a centered and well defined 6-rayed star. The curved growth is especially visible on the flat base of the stone. The stones might have gas bubbles and minute rutile needles that make up the star will confined to the surface of the stones.
Stability
Excellent
Lab Created Czochralski Star
Synthetic star ruby exhibits the optical phenomenon called asterism, a star-like pattern created on the surface of a gemstone when light encounters parallel fibrous, or needle-like, inclusions within its crystal structure. Light that strikes the inclusions within the gem reflects off of the inclusions, creating a narrow band of light. When two or more intersecting bands appear, a star pattern is formed. The Czochralski process of gem synthesis involves the melting of various elements in a platinum crucible. A small gem crystal (called a seed) attached to a rod is then dipped into the melt and slowly pulled away as the crystal grows around the seed. For this reason, the Czochralski method is also known as crystal pulling. Synthetic gems have the same chemical, optical, and physical properties of their natural counterparts, but are a more cost-effective alternative to a natural gem.
- Classification
- Characteristic Physical properties
Common Name
Lab Created Czochralski Star
Specific Gravity
3.950
Toughness
Good
Inclusions
Pulled synthetic star ruby will have extremely fine needles that produce a slightly wavy natural looking 6-rayed star. The stones typically show low-relief curved striae or wavy growth. Sometimes bluish white smoke-like swirls and small round or distorted blackish gas bubbles are seen in stones.
Stability
Excellent
Material Combination
Lab Created Ruby Overgrowth on Natural Corundum Seed
Synthetic ruby overgrowth corundum has a layer of lab created ruby grown on a colorless corundum.
- Classification
- Characteristic Physical properties
Common Name
Lab Created Ruby Overgrowth on Natural Corundum Seed
Specific Gravity
3.950
Toughness
Good
Inclusions
Color on these stones is strong table up but patchy on the pavilion when viewed on a white piece of paper. The stones have wavy growth that can appear step like or crystalline. One might be able to see facet junctions of the original stone underneath the overgrowth layer that do not match the facets of the outer layer. Stones will probably show uneven color due to removal or the overgrowth layer. They have a mottled or roiled texture when stone is viewed with immersion.
Stability
Good
Enhancement
Flux Healed
Flux healed rubies have been heated in the presence of a flux material like borax. The flux will penetrate fissures in the stone and will act like a catalyst to heal the fracture in the stone. The flux will help melt the surrounding ruby to fill in the fissure and improve the clarity in the stone.
Flux Healed Ruby
- Classification
- Optical Properties
- Characteristic Physical properties
Common Name
Flux Healed
CCF Reaction
red
Specific Gravity
3.950
Toughness
Excellent
Inclusions
Flux like residue in fissure. It will not be as thick as flux grown rubies. It might have small air bubbles in fissure.
Stability
Excellent
Lead Glass Filled
Lead glass filled rubies have been filled through a process similar to "infilling" using lead glass. Performed at lower temperatures, this is a less durable treatment and should be treated gently, avoiding household and professional chemicals. This treatment improves clarity, color, durability, and may add weight through the filling of voids and fissures.
Lead Glass Filled Ruby
- Classification
- Characteristic Physical properties
Common Name
Lead Glass Filled
Specific Gravity
3.950
Toughness
Poor
Inclusions
Lead glass filled rubies will show gas bubble sand color concentrations in fissures. Blue flash colors from the lead glass filling might be seen when viewing stone in dark field lighting.
Stability
Poor
