Spinel

saf-ahyuh r

Naturally dazzling spinel has graced the pages of history and many royal crowns due to its resemblance to ruby. Today, however, spinel stands on its own as a remarkable gem. Spinel comes in a wide range of stunning hues and can also exhibit optical phenomena like asterism and color-change. It is generally underappreciated compared to other colored stones, lending itself to more affordable prices, but this gem, said in Burma to be polished by the spirits, has a beauty that is difficult to ignore.

Spinel Polished
Spinel Classification
Common Name Spinel
Species Spinel
Spinel Optical Properties
Transparency Transparent - Opaque
Dispersion Strength: Moderate Fire Value: 0.02
Refractive Index 1.718
Optic Character NA
Optic Sign NA
Polariscope Reaction Singly Refractive (SR) With ADR
Fluorescence SWUV: Variable
LWUV: Variable
CCF Reaction Pink to red: inert to fluorescent red. Rare blue with cobalt: reddish inert if iron type
Spinel Characteristic Physical Properties
Hardness 8
Specific Gravity 3.570-3.700 Range:0.1/-0.03 Typical:3.600
Toughness Varies
Inclusions Spinel is a type II clarity stone. Stones might contain natural mineral inclusions like spinel or apatite, needles, negative crystals in the shape of an octahedral, fingerprints and iron oxide staining.
Luster SubAdamantine, Vitreous
Stability Very Good
Fracture Conchoidal
Cleavage None
Spinel Chemistry & Crystallography
Chemical Name magnesium aluminum oxide
Chemical Formula MgAl2O4
Crystal System Cubic
Chemistry Classification Oxide

Spinel Colors

  • Black Spinel Black
  • Orange Spinel Orange
  • Yellow Spinel Yellow
  • Green Spinel Green
  • Gray Spinel Gray
  • Colorless Spinel Colorless
  • Brown Spinel Brown

Spinel Spectra

Spinel Spectra
SPINEL

Color due to chromium. Two fine lines and weak band in red. Very faint general absorption of the yellow and green

Spinel Spectra
SPINEL - Verneuil Synthetic blue

The cobalt spectrum produced by synthetic blue spinel is very similar to that seen in cobalt blue glass but with certain variations. The band in the green is centered at 540nm., the band in the yellow is centered at 580nm. and the band in the red is centered at 635nm. This gives the appearance of the three bands being closer together compared to the spectrum in blue glass. Note also that here the center band in the yellow is broader than the other two.

Spinel Spectra
SPINEL - Verneuil Synthetic blue

Color due to cobalt. As the cobalt content increases in synthetic blue spinel, the stone appears a deep cobalt blue and the spectrum shows broader and darker absorption bands. The one at 540nm. may merge with the one at 580nm. to form a wide dark area in the green. Here a faint narrow transmission window is seen at about 500nm.

Spinel Spectra
SPINEL – Lab Created RED GAHNITE (Fluorescence spectrum)

By a slight alteration to the orientation of the stone, in relation to the direction of the light source, the full impact of the fluorescing emission lines can be seen. The strongest at 686nm. is supported by another eight lines, three on the long wave side and five more on the short-wave side

Spinel Spectra
SPINEL – Lab Created RED GAHNITE

Color due to chromium. With the strong central absorption band eliminating all green and yellow light. Only the very hint of thin vague emission lines are detected, with difficulty, in the red and are easily missed in this transmitted absorption spectrum

Spinel Spectra
SPINEL.(Fluorescence spectrum)

The fluorescence spectrum of this spinel is more convincing than the absorption spectrum. Here we see the series of emission lines often referred to as the "Organ Pipe" pattern where the strongest line at 686nm. is prominently displayed. Paler red spinels may display this whole series of emission lines even more strongly. These emission lines can be detected as seen here in scattered light conditions

Spinel Spectra
SPINEL - RUSSIAN FLUX lab created (Fluorescence spectrum)

In the early Verneuil stones and in most of the modern flux grown stones, the fluorescent lines in the red are less easily defined and mainly dominated by the single line at 686nm

Spinel Spectra
SPINEL - RUSSIAN FLUX Lab Created

Color due to chromium. The absorption spectrum of lab Created red spinel is very similar to the natural counterpart with the main line in the red usually only detected as an emission line. The width of the central absorption band will vary according to the depth of color.

Spinel Spectra
SPINEL

Color due to chromium. The broad absorption due to chromium in spinel is centered at 540nm. A little blue is transmitted but absorption takes over again from about 480nm. The lighter bright red spinel’s, lines in the red part of the spectrum are rarely detected in this dark red variety

Spinel Spectra
SPINEL

Color due to chromiumIn this bright orange - red variety of spinel the doublet in the red at 685/684nm. may be seen but often difficult to detect as absorption lines. However, the absence of lines in the blue, and the broad band in the green being centered more towards the short-wave side at 540nm. than in ruby, (550nm.) is sufficient to distinguish between these two gemstones

Spinel Spectra
SPINEL

Color due to chromium. Spinel in this particular pinkish red hue can easily be confused with a fine ruby. Three features in the spectrum can help to separate the two stones. The first is the absence of the lines in blue area. The second, perhaps less obvious, is the position of the central absorption band which is centered at 440nm. compared to 550nm. in ruby. Finally, in the absorption spectrum lines in the red are difficult to detect, but the bright emission line at 686nm., is noticeably further away from the long wave end compared to ruby at 693/694nm

Spinel Spectra
SPINEL(Fluorescence spectrum)

Manipulation of the stone in a high intensity light can reveal several other emission lines in the red. Often referred to as an "Organ pipe" pattern .This can be detected to a limited degree by scattered light but is best seen under crossed color filters where the majority of the series of about ten lines may be seen. Only five are seen here due to the transmission of the accompanying orange-red light, one on the long wave side and three on the short-wave side of the strongest line at 686nm

Spinel Spectra
SPINEL Flux grown synthetic

Color due to cobalt. The spectrum of this Russian flux grown spinel shows an intense three band cobalt spectrum with a narrow transmission window in the green.

Spinel Spectra
Spinel Greenish Blue

Color mainly due to iron. This spectrum from a dark blue spinel illustrates how absorption is stronger as the color becomes deeper and more saturated. The spectrum pattern is similar to a lighter blue, but here all the bands are now broader and darker especially the iron band at 460nm. Note there is very little transmission beyond 630nm.

Spinel Spectra
SPINEL Greenish Blue

Color due to iron. A slight green overtone in the light blue spinel that provided this spectrum is not unlike a sapphire but the single band in the blue is further to the long wave side at 460nm. as opposed to 450nm in sapphire. Two other broad diffuse bands can be seen centered at 560nm. and 585nm. then total absorption beyond 650nm.

Spinel Spectra
SPINEL Blue

Color due to cobalt and iron.This spectrum is from a less vibrant blue spinel but still has no green overtone due to the very weak iron line at 460nm. And the cobalt bands are weaker with less transmission in the deep red.

Spinel Spectra
SPINEL Blue

Color mainly due to cobalt. Spinel is seldom a fine blue comparable with sapphire and is usually seen with a dark green overtone due to ferrous iron. When a high cobalt content is present with very little iron, as in the spectrum of the stone shown here, a finer blue is achieved. In the spectrum the absorption line associated with ferrous iron at 460nm. is extremely faint. This and the three bands due to cobalt make it not unlike the spectrum seen in synthetic flux grown spinel but there would be no iron line at 460nm. in the synthetic.

Spinel Spectra
SPINEL Blue

Color due to cobalt and iron. The iron line at 460nm. is distinct but the stone is still a good blue color. The cobalt bands are present but there is little transmission beyond 650nm.

Spinel Spectra
SPINEL Greenish blue

Color due to iron and cobalt. A very dark greenish blue spinel provides a spectrum with a strong iron band at 460nm. It also shows three cobalt bands in the green yellow and orange areas. Very little transmission is seen from 540nm. to 610nm. but note the two very narrow windows at 555nm. and 585nm.

Spinel Spectra
SPINEL

Color due to iron. The spectrum of this almost colorless spinel with the slightest tint of lavender blue yields little to help identity. However, on careful inspection a very fine line can be seen at 460nm. in the blue. The two faint bands centered at 570nm. and 590nm. create a delicate balance which enables a slight color shift to a lilac pink in tungsten light.

Spinel Spectra
SPINEL

Color due to chromium. Fine lines or bands in the red. General absorption in yellow and green. The width and darkness of the absorption bands varies. The number of lines seen in the red may vary, in some stones they may appear as a doublet or as emission lines. There are usually no lines visible in the blue

Jewelry Television acknowledges 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

Flame Spinel, Rubicelle, Ceylonite, Pleonaste, Alumag, Corundolite, Lustergem, Magalux, Radient, Strongite ,Wesselton, Simulated Diamond, Aquagem, Rozircon, Berylite, Dirigem, Perigem, Emerada, Erinide

Countries of Origin

Tanzania, United Republic Of; Myanmar; Afghanistan; Viet Nam; Cambodia; Madagascar; Thailand; Mozambique; Pakistan; Unknown; China; Russian Federation (the); Brazil; Nigeria; Romania; United States of America (the); Sri Lanka; Switzerland; Bolivia (Plurinational State of); India; Canada; Namibia; Venezuela (Bolivarian Republic of); Germany; Tajikistan

History

It's been called the great impostor, because historically it's been mistaken for other stones. For example, some of the most famous rubies in history aren't rubies. They're spinel. We feel this does a disservice to spinel. Spinel deserves to stand on its own; to be recognized for what it is. Delightfully dazzling, this stone is one of the under-sung beauties of the jewelry world. Spinel is not an impostor - spinel has always been spinel. It's just that, for many centuries, we didn't know it. Today, we do know spinel, and a fine stone it is - hard, wonderfully wearable, sparkling, and available in a variety of colors.Treat yourself to spinel today. At JTV®, we have a wide range of choices in beautiful, affordable spinel.

Shop Spinel

Related Videos

More About Spinel

Much of the history of ruby is actually history written around spinel that was thought to be ruby In some cultures, it was believed that spinel could protect a person from the evil-eye; in other cultures, it was thought to provide protection. For many centuries, spinel was associated with power, fire, and life. Folklore... it doesn't have any scientific support, but it certainly has fascination.

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Creation Method

Flux Lab Created

One method of creating synthetic spinel 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.

Flux Lab Created Spinel
Flux Lab Created Classification
Common Name Flux Lab Created
Flux Lab Created Optical Properties
Dispersion Strength: weak fire Value: 0.02
Refractive Index 1.719
Tolerance:(+0.003/-0.003)
CCF Reaction Blue: red to orangy red
Pleochroism None
Flux Lab Created Characteristic Physical properties
Specific Gravity 3.58
Inclusions Flux-grown spinel typically has flux residue inclusions that can be orangy brown to black in color. Some flux inclusions are singular but others can be mistaken for fingerprint inclusions. Stones might contain metallic platelets from the platinum crucible. Dark blue stones might show a red flash under penlight due to cobalt coloring agent.

Flame Fusion Lab Created

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.

Flame Fusion Lab Created Spinel
Flame Fusion Lab Created Classification
Common Name Flame Fusion Lab Created
Flame Fusion Lab Created Optical Properties
Dispersion Strength: weak fire Value: 0.02
Refractive Index 1.722-1.728
Tolerance:-1.5
CCF Reaction synthetic blue spinel produces a strong red reaction
Pleochroism None
Flame Fusion Lab Created Characteristic Physical properties
Inclusions Flame-fusion spinel may contain thread like or angular gas bubbles. Red stones might show curved striae growth patterns or color banding but this is rare. Strongly saturated blue stones might show red flashes due to cobalt as coloring agent.

Species/Variety

Gahnospinel

Gahnospinel is the rare violetish to dark blue, zinc-rich variety of spinel. A variety of spinel rich in zinc, much of the world's supply of gahnospinel comes from Sri Lanka. Since gahnospinel is chemically midway between spinel and gahnite, hence its name is a combination of the two. The first half is in honor of Johann Gottlieb Gahn, a Swedish chemist and mineralogist.

Gahnospinel Spinel
Gahnospinel Classification
Common Name Gahnospinel
Gahnospinel Optical Properties
Refractive Index 1.76
Tolerance:(+0.020/-0.020)
Fluorescence SWUV: Inert
LWUV: Inert
Pleochroism None
Gahnospinel Characteristic Physical properties
Specific Gravity 3.61

Gahnite

Ranging from dark green to black in color, gahnite is a rare member of the spinel group. It was first discovered in Sweden 1807 and named in honor of Swedish chemist J.G. Gahn, who is credited with the discovery of manganese. While highly prized by mineral collectors for its octahedral crystal formation, gahnite is on occasion cut into faceted gems.

Gahnite Spinel
Gahnite Classification
Common Name Gahnite
Gahnite Optical Properties
Refractive Index 1.8
Tolerance:(+0.005/-0.010)
Pleochroism None
Gahnite Characteristic Physical properties
Specific Gravity 4.4

Optical Phenomena

Color Change

Along with a rich range of hues, spinel offers color-change varieties. Color change spinel usually appears violet blue under fluorescent light and purple under incandescent light. Spinel is one of few gemstones that require no special treatments; its beautiful, vivid colors and clarity are entirely natural. Spinel is also excellent for use in jewelry because it is hard, tough, and often more affordable than ruby or sapphire.

Color Change Spinel
Color Change Classification
Common Name Color Change
Color Change Optical Properties
Dispersion Strength: weak fire Value: 0.02
Refractive Index 1.718
Tolerance:(+0.017/-0.008)
Fluorescence SWUV: Inert
LWUV: Moderate to strong chalky red
Pleochroism None
Color Change Characteristic Physical properties
Inclusions Natural mineral inclusions like spinel or apatite, needles, negative crystals in the shape of an octahedral, and fingerprints.

Star

Star spinel 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. Depending on the crystal, the star may have four, six, or even twelve rays. When only one band forms, it is classified as a "cat's eye". Star spinel is highly treasured by collectors for its phenomenal quality.

Star Spinel
Star Classification
Common Name Star
Star Optical Properties
Refractive Index 1.718
Tolerance:(+0.017/-0.008)
Pleochroism None
Star Characteristic Physical properties
Inclusions Star spinels will contain needles that may show six or four rayed star. In stones cut as spheres it might be possible to see both four and six rayed stars. Stones might contain natural mineral inclusions like spinel or apatite, negative crystals in the shape of an octahedral and fingerprints.
Tim Matthews

Author

Tim Matthews

Tim Matthews is President and Chief Executive Officer of Jewelry Television® (JTV), as well as a member of the company's Board of Directors. He oversees and leads all aspects of the company's powerful omni-digital retail platform that uniquely specializes in fine jewelry and gemstones. His passion for business and gemstones has led him to become a recognized expert in the field of gemology. He is a life member of the Gemmological Association of Great Britain (Gem-A) and has earned Gem-A's highest degrees, the Gemmology (FGA) and Diamond (DGA) diplomas. He is also a Graduate Gemologist (GG) of the Gemological Institute of America (GIA) and has also completed GIA's Graduate Diplomas in Diamonds, Colored Stones and Pearls. Under his leadership, JTV has become the leader in the sourcing and selling of color gemstones and jewelry.

This page was created on June 27, 2014.

This page was last edited on October 24, 2019.