Scope
This entry lists gemstone species commonly encountered in the retail rough market. Descriptions cover chemical composition, Mohs hardness, principal sources of commercial rough, and typical treatments. The entry does not constitute instruction in faceting any species; cutting parameters are published by the designer of the individual cut and by the species-specific literature.
Quartz family
The quartz family includes amethyst (purple), citrine (yellow to orange), smoky quartz (brown), rose quartz (pink), and rock crystal (colorless). All members share a composition of silicon dioxide and a Mohs hardness of 7.
Commercial rough is produced in Brazil, Uruguay, Zambia, and Madagascar. Citrine of commercial grade is typically produced by heat treatment of amethyst or smoky quartz precursors; this treatment is standard and is not always declared on retail listings.
Beryl family
The beryl family includes aquamarine (blue to blue-green), morganite (pink to orange-pink), heliodor (yellow), goshenite (colorless), and emerald (green). Composition is beryllium aluminum silicate; Mohs hardness is 7.5 to 8.
Aquamarine is commonly heat-treated to remove green overtones. Emerald is frequently oiled or resin-filled to fill surface-reaching fractures; these treatments are detectable in the laboratory and are often declared on higher-end retail listings.
Corundum
Corundum is the mineral species that includes ruby (red) and sapphire (all other colors). Composition is aluminum oxide; Mohs hardness is 9. Rough is produced in Sri Lanka, Madagascar, Mozambique, Kenya, Montana, and Thailand.
Treatment conventions for corundum are varied and material-specific. Heat treatment, fracture filling, and lattice diffusion are all in commercial use; disclosure requirements vary by jurisdiction and seller.
Tourmaline
Tourmaline is a group of related complex silicate minerals. The elbaite series covers the widest commercial color range (green, pink, red, blue, and bicolor). Mohs hardness is 7 to 7.5.
Commercial rough is produced in Brazil, Nigeria, Mozambique, Afghanistan, and Madagascar. The Paraíba variety, distinguished by copper content and an electric blue-green color, commands a significant price premium.
Topaz
Topaz is aluminum silicate with fluorine and hydroxyl; Mohs hardness is 8. Natural colors range from colorless to pale blue, yellow, and brown; more saturated blues on the market are typically produced by irradiation followed by heat treatment.
Commercial rough is produced in Brazil, Nigeria, Pakistan, and Russia. The imperial topaz variety (golden orange to sherry red) is associated principally with Ouro Preto, Brazil.
Garnet group
The garnet group comprises a family of silicate minerals of varying composition. Common gem-grade species include almandine, pyrope, spessartine, grossular (including tsavorite), and andradite (including demantoid). Mohs hardness across the group is 6.5 to 7.5.
Garnets are typically not heat-treated. Rough is produced in East Africa (Kenya, Tanzania, Madagascar), Brazil, Namibia, and Russia.
Peridot
Peridot is the gem variety of the mineral forsterite-fayalite (magnesium iron silicate). Mohs hardness is 6.5 to 7. Commercial rough is produced in Arizona, Pakistan, Myanmar, and China.
Note on disclosure
Facetting.com reproduces seller-supplied descriptions without independent verification. Prospective purchasers who require authenticated origin, weight, or treatment status should request laboratory certification from a recognized gemmological institute prior to purchase.