A-Z of Gemstones

Alexandrite and Other Chrysoberyls

• Hardness: 8.5
• Toughness: Excellent
• Lustre: Vitreous
• Colour: Green to red (alexandrite), yellow to green (chrysoberyl)
• Cutting Styles: Ovals, cushions, cat's eye (chatoyancy)
• Discovered: 1830s (Russia)
• Crystal System: Orthorhombic

Amethyst

• Hardness: 7
• Toughness: Fair to good
• Lustre: Vitreous
• Colour: Light lilac to deep purple
• Cutting Styles: Rounds, ovals, antique step cuts
• Crystal System: Trigonal

Aquamarine

• Hardness: 7.5-8
• Toughness: Good
• Lustre: Vitreous
• Colour: Light to deep blue
• Cutting Styles: Emerald cuts, ovals, step cuts
• Crystal System: Hexagonal

Other Beryls (Morganite, Heliodor, Goshenite)

• Hardness: 7.5-8
• Toughness: Good
• Lustre: Vitreous
• Colour: Pink, yellow, colourless
• Cutting Styles: Mixed, step, brilliant
• Crystal System: Hexagonal

Chalcedony

• Hardness: 6.5-7
• Toughness: Excellent
• Lustre: Waxy to dull
• Colour: Pale blue, grey, lavender
• Cutting Styles: Cabochons, intaglios, cameos
• Crystal System: Trigonal (microcrystalline quartz)

Citrine

• Hardness: 7
• Toughness: Good
• Lustre: Vitreous
• Colour: Pale yellow to amber
• Cutting Styles: Step and brilliant cuts
• Crystal System: Trigonal

Emerald

• Hardness: 7.5-8
• Toughness: Poor to fair
• Lustre: Vitreous
• Colour: Deep green to bluish green
• Cutting Styles: Emerald cut, ovals
• Crystal System: Hexagonal

Feldspar Group (Moonstone, Labradorite, Sunstone)

• Hardness: 6-6.5
• Toughness: Poor to fair
• Lustre: Vitreous to pearly
• Colour: Various (blue, peach, green, iridescent)
• Cutting Styles: Cabochons, fancy shapes
• Crystal System: Monoclinic (orthoclase), Triclinic (plagioclase)

Garnet Group

• Hardness: 6.5-7.5
• Toughness: Good
• Lustre: Vitreous to resinous
• Colour: Red, green, orange, pink
• Cutting Styles: Antique rose cuts, rounds, ovals
• Crystal System: Isometric

Jade and Nephrite

• Hardness: 6-7
• Toughness: Excellent
• Lustre: Greasy to waxy
• Colour: Green, white, lavender
• Cutting Styles: Cabochons, carvings
• Crystal System: Jadeite: Monoclinic; Nephrite: Monoclinic (amphibole group)

Kunzite

• Hardness: 6.5-7
• Toughness: Poor
• Lustre: Vitreous
• Colour: Pale pink to violet
• Cutting Styles: Emerald and step cuts
• Discovered: Early 20th century
• Crystal System: Monoclinic

Lapis Lazuli

• Hardness: 5-6
• Toughness: Fair
• Lustre: Waxy to dull
• Colour: Deep royal blue with pyrite inclusions
• Cutting Styles: Cabochons, plaques
• Crystal System: Not a single mineral - mainly Lazurite (isometric)

Opal

• Hardness: 5.5-6.5
• Toughness: Poor
• Lustre: Vitreous to pearly
• Colour: Milky white to black with play-of-colour
• Cutting Styles: Cabochons, freeforms
• Crystal System: Amorphous (not crystalline)

Organic and Biogenic Gem Materials

Includes pearl, amber, coral, jet

• Hardness: Varies (2.5-4.5)
• Toughness: Generally poor
• Lustre: Pearly, resinous, dull
• Colour: White, cream, black, red, golden, brown
• Cutting Styles: Beads, cabochons, carvings
• Crystal System: Organic - no defined crystal structure

Peridot

• Hardness: 6.5-7
• Toughness: Fair
• Lustre: Vitreous
• Colour: Olive to lime green
• Cutting Styles: Ovals, rounds, step cuts
• Crystal System: Orthorhombic

Quartz Group (Rose Quartz, Smoky Quartz, Rock Crystal)

• Hardness: 7
• Toughness: Good
• Lustre: Vitreous
• Colour: Colourless, pink, brown, grey
• Cutting Styles: Brilliant, step cuts, cabochons
• Crystal System: Trigonal

Ruby

• Hardness: 9
• Toughness: Excellent
• Lustre: Vitreous
• Colour: Red to purplish red
• Cutting Styles: Cushion, oval, mixed cuts
• Crystal System: Trigonal

Sapphire

• Hardness: 9
• Toughness: Excellent
• Lustre: Vitreous
• Colour: Blue, yellow, green, pink, colourless
• Cutting Styles: Ovals, step cuts, cabochons (star sapphires)
• Crystal System: Trigonal

Spinel

• Hardness: 8
• Toughness: Good
• Lustre: Vitreous
• Colour: Red, pink, violet, blue
• Cutting Styles: Ovals, antique brilliant cuts
• Crystal System: Isometric

Tanzanite

• Hardness: 6-7
• Toughness: Poor to fair
• Lustre: Vitreous
• Colour: Blue to violet-blue
• Cutting Styles: Emerald and step cuts
• Discovered: 1967
• Crystal System: Orthorhombic

Topaz

• Hardness: 8
• Toughness: Poor (perfect cleavage)
• Lustre: Vitreous
• Colour: Blue, yellow, pink, golden, clear
• Cutting Styles: Ovals, pears, emerald cuts
• Crystal System: Orthorhombic

Tourmaline

• Hardness: 7-7.5
• Toughness: Good
• Lustre: Vitreous
• Colour: All colours, often bi-colour
• Cutting Styles: Fancy cuts, cabochons (cat's eye)
• Crystal System: Trigonal

Turquoise

• Hardness: 5-6
• Toughness: Fair
• Lustre: Waxy to dull
• Colour: Sky blue to green
• Cutting Styles: Cabochons, beads
• Crystal System: Triclinic

Zircon

• Hardness: 6-7.5
• Toughness: Fair
• Lustre: Adamantine
• Colour: Blue, brown, yellow, red, green, clear
• Cutting Styles: Round brilliant, antique cushion
• Crystal System: Tetragonal