* corundum gemstone
Ruby: identification, value, and how to spot a fake
Chromium impurity gives red color. Burmese (Myanmar) 'pigeon's blood' rubies command the highest prices. Most market rubies are heat-treated; untreated stones with lab reports premium dramatically.
Published May 30, 2026
Quick facts
- Mineral family
- corundum
- Chemical formula
- Al2O3 (Cr impurity)
- Mohs hardness
- 9
- Refractive index
- 1.762–1.77
- Specific gravity
- 3.97–4.05
- Crystal system
- trigonal
- Luster
- vitreous
- Dispersion
- 0.018
- Birthstone month
- July
Colors
Ruby is found in red, pinkish-red, purplish-red. The body color, its saturation, and how evenly it spreads through the stone are among the strongest drivers of value.
How to tell real from imitation
No single test settles it, but a few grounded checks quickly narrow things down for Ruby. Hardness, brilliance, and the list of stones it is commonly confused with all give you something concrete to look for.
- Scratch resistance: genuine Ruby sits at Mohs 9, so it should resist scratching from softer materials — a stone that mars far too easily is suspect.
- Brilliance & luster: Ruby shows a vitreous luster and a refractive index of 1.762–1.77; imitations often look glassier or flatter under the same light.
- Density: a real Ruby has a specific gravity near 3.97–4.05, so it feels heavier or lighter in the hand than many look-alikes of the same size.
- Commonly imitated by: red garnet, red spinel, red tourmaline, glass, synthetic ruby. If a deal looks too good, suspect one of these substitutes first.
- Fast first read: photograph the stone in the Jewelry Identifier app to estimate the gemstone and its likely value range, then confirm anything important with a gemological lab.
Common treatments
- heat treatment (near-universal)
- lead-glass fracture filling
- diffusion treatment
Treatments are routine for many Ruby stones, but they materially affect value and should always be disclosed — an untreated, lab-certified stone commands a clear premium over a treated one.
What to know about Ruby
Chromium impurity gives red color. Burmese (Myanmar) 'pigeon's blood' rubies command the highest prices. Most market rubies are heat-treated; untreated stones with lab reports premium dramatically.
Sources
* Frequently asked
FAQ
- Q. Is Ruby hard enough for everyday rings?
- A. Yes. At a Mohs hardness of 9, Ruby is durable enough for daily-wear rings; it resists the scratches that everyday surfaces inflict.
- Q. How can I tell Ruby from red garnet?
- A. Ruby and red garnet can look alike to the naked eye, but they differ in measurable properties — refractive index (1.762–1.77 for Ruby), specific gravity (3.97–4.05), and hardness (Mohs 9). A gemologist confirms the distinction with a refractometer and loupe; the Jewelry Identifier app gives a fast first read from a photo.
- Q. Does Ruby come in colors other than red?
- A. Yes. Ruby occurs in red, pinkish-red, purplish-red. Color is driven by trace elements and treatment history, and it is one of the biggest factors in a stone's value.
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