Species and variety

Many well-known gemstone names do not denote separate minerals but varieties. The laboratory report therefore distinguishes between species and variety.

Species: the mineralogical identity

The species describes the mineral with its chemical composition and crystal structure. Corundum is aluminium oxide, beryl a beryllium aluminium silicate, chrysoberyl a beryllium aluminium oxide. The species determines the basic properties, such as hardness and refractive index.

Variety: the traded form

The variety denotes a recognised form within a species, usually determined by colour or an optical phenomenon:

• Corundum: ruby (red) and sapphire (all other colours; without qualifier, blue)
• Beryl: emerald (green, due to chromium and/or vanadium), aquamarine (blue), morganite (pink)
• Chrysoberyl: alexandrite (with colour change), cat's-eye (with a band of light)
• Tourmaline: Paraíba tourmaline (blue to green, due to copper and manganese)

Where the boundary is difficult

Variety boundaries are not always sharp. At what saturation a pink corundum counts as ruby is not judged the same everywhere. For emerald, specialists debate whether vanadium alone suffices as the cause of colour. For Paraíba tourmaline, the LMHC has defined the name as applying to blue to green tourmaline coloured by copper and manganese – regardless of origin.

Why this matters to you

The variety has a considerable effect on value. A ruby is valued differently from a pink sapphire, even if the difference in colour is small. It is therefore worth knowing the wording in the report and the criteria of the issuing laboratory.

Trade names

Terms such as "padparadscha" are variety names with their own definitions, which can differ between laboratories. Other names, such as "Kashmir blue", describe a colour impression rather and must not be confused with a statement of origin.

In brief

The species describes the mineral, the variety its traded form, usually by colour. The boundaries between varieties are not defined the same everywhere. Knowing the issuing laboratory's criteria allows the statement to be placed correctly.

At NOBILITH

The dossier states species and variety as in the laboratory report. The Academy masterclasses explain for each species which varieties exist and how they differ.

Sources

• LMHC: Information Sheets, including on Paraíba tourmaline and padparadscha
• CIBJO: The Gemstone Book