Gem Property Ranker

Rank all gemstones by any property — hardness, price, refractive index, specific gravity, or dispersion.

Comparison
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How to Use

  1. 1
    Choose a property to rank gems by

    Select from available ranking criteria including Mohs hardness, refractive index, specific gravity, and dispersion. Each property provides a different perspective on gem characteristics, from practical durability to optical beauty.

  2. 2
    Filter by gem category if desired

    Narrow the ranking to a specific category such as precious stones, semi-precious stones, organic gems, or synthetics. This helps compare gems within the same market tier or intended use case.

  3. 3
    Read and interpret the ranked results

    Review the ranked list with values displayed alongside gem names. Use the rankings to identify which gems excel in specific properties—for example, diamond tops hardness rankings while demantoid garnet leads in fire (dispersion) among natural gems.

About

Ranking gemstones by physical and optical properties provides a systematic way to understand which stones excel for particular purposes. The Mohs hardness scale, introduced by Friedrich Mohs in 1812, remains the most widely used relative hardness ranking, though it is ordinal rather than linear—corundum at 9 is roughly twice as hard as topaz at 8, and diamond at 10 is roughly four times harder than corundum. Complementary measures including absolute hardness (Vickers, Knoop) and toughness provide a more complete durability picture.

Optical property rankings reveal why certain gems command premiums. Refractive index determines how much a properly cut stone will sparkle, while dispersion determines fire (rainbow flashes). A gem cutter optimizes a stone's proportions to maximize these effects based on the specific RI of the material—ideal angles for diamond differ from those for sapphire or quartz. The GIA and other institutions have established standard cut grades based on these optical physics, and understanding the underlying properties helps appreciate why some cuts unlock a gem's potential while others waste it.

Specific gravity rankings assist identification and give insight into a gem's composition. Dense gems like zircon, corundum, and chrysoberyl feel noticeably heavier than lighter stones of the same size. This tactile difference was historically used by gem traders before modern testing equipment existed. Today, hydrostatic weighing provides precise SG measurements in minutes, making this one of the most accessible gemological tests alongside refractive index measurement with a refractometer.

FAQ

Which natural gemstone has the highest refractive index?
Diamond has the highest refractive index (RI) of any natural gemstone at approximately 2.417–2.419, which is a primary reason for its exceptional brilliance. Among colored gems, demantoid garnet (2.88) and sphene/titanite (1.885–1.990) have notably high RIs. Synthetic moissanite has an even higher RI (2.65–2.69) than diamond, which is one reason it is used as a diamond simulant, though its optical behavior differs in other ways.
What does specific gravity tell you about a gemstone?
Specific gravity (SG) measures a gem's density relative to water. Most gems range from about 2.6 (quartz) to 4.0 (zircon), with some dense exceptions like cinnabar at 8.0. Specific gravity is one of the most reliable identification tools in gemology because it is measured objectively using hydrostatic weighing. A heavier gem for its size indicates higher SG; for example, a ruby (SG 3.97–4.05) feels noticeably denser than a similarly sized piece of glass (SG ~2.5). SG measurement helps distinguish natural gems from imitations and from each other.
Why do some gems with lower hardness remain popular in jewelry?
Hardness is only one factor in a gem's practicality and appeal. Opal (Mohs 5.5–6.5), turquoise (5–6), and pearl (2.5–4.5) remain beloved despite their relative softness because of unique optical effects—opal's play of color, turquoise's distinctive sky blue, and pearl's orient—that cannot be replicated in harder stones. Protective settings, careful wearing habits, and proper storage can compensate for lower hardness. Additionally, some soft gems like emerald (7.5–8) are valued so highly for their color that their brittleness (due to typical inclusions) is accepted.
Which gem has the strongest fire or dispersion?
Fire in gemology refers to dispersion: the gem's ability to split white light into spectral rainbow colors. Diamond has a dispersion value of 0.044, but demantoid garnet (0.057) and sphene (0.051–0.057) actually exceed diamond in fire. Synthetic moissanite (0.104) and synthetic rutile (0.330) show dramatically more fire than diamond, sometimes appearing garish to trained eyes. Among well-known colored stones, zircon (0.039) and tanzanite show notable fire. The combination of high RI and high dispersion in a well-cut stone produces the most visually spectacular results.
How does the hardness ranking differ from the toughness ranking?
The Mohs hardness scale measures only scratch resistance and does not reflect fracture resistance. Diamond, the hardest natural substance at 10, has perfect cleavage in four directions, making it susceptible to splitting with an angled blow. Jadeite and nephrite jade rank only 6–7 on the Mohs scale but are among the toughest gems due to their interlocking crystal structures. Corundum (ruby and sapphire, Mohs 9) has excellent toughness with no cleavage, combining high hardness with fracture resistance—making it superior to diamond for some practical applications despite lower hardness.
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