What is the Mohs hardness scale?

The Mohs scale ranks a mineral's scratch resistance from 1 (talc) to 10 (diamond). Each step means the higher mineral scratches the lower. Hardness alone does not identify a gem, but it helps narrow candidates and indicates durability for jewellery.

How does refractive index help identify gemstones?

Refractive index (RI) measures how much a stone bends light and is one of the most reliable identifiers. Measured on a refractometer, an RI reading combined with hardness, specific gravity and optical character usually pins down the species.

What is specific gravity?

Specific gravity (SG) is a stone's density relative to water. A 3.52 SG diamond feels heavier than a same-size 2.66 quartz. Gemmologists measure it by hydrostatic weighing or heavy-liquid testing to support identification.

Is a higher Mohs hardness always better for jewellery?

Generally yes for durability, but toughness also matters. Diamond is hardest (10) yet can cleave on impact, while jade is softer (around 6.5) but extremely tough. For rings, a hardness of 7 or above resists everyday scratching well.

Does this reference work offline?

Yes. The full gemstone property table is built into the page and filtering runs entirely in your browser. Nothing is uploaded or stored.

Gemstone Properties Reference

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Comparing gemstones by their properties

Every gem species has a characteristic set of physical properties: Mohs hardness, refractive index (RI), specific gravity (SG) and crystal system. Together these let a gemmologist separate look-alike stones — for example a real diamond from cubic zirconia, or a sapphire from a blue spinel.

How it works

Hardness is a 1–10 scratch-resistance scale (diamond = 10). Refractive index, read on a refractometer, measures how strongly the stone bends light and is one of the single most diagnostic figures. Specific gravity is density relative to water, measured by hydrostatic weighing. The crystal system (cubic, hexagonal, trigonal, tetragonal, orthorhombic, monoclinic, triclinic, or amorphous) reflects the internal atomic arrangement and predicts optical behaviour.

This reference lists 50+ gemstones with all four properties. The search box filters every column, so you can look up a stone by name or shortlist candidates by a measured value.

Tips and example

Suppose a colourless stone reads RI 1.62, hardness 8 and SG 3.60. Scanning the table points to topaz rather than diamond (RI 2.42, SG 3.52) or quartz (RI 1.55, SG 2.65). No single property is conclusive — combine RI, hardness and SG, and confirm with a gemmologist for valuable stones.