Rubies, sapphires, emeralds and beyond — compare colour ranges, cuts, hardness, clarity and care for the world’s most loved gemstones, all in one place.
Hue, Tone and Saturation
Colour is the single most important quality of a coloured gemstone. Gemmologists describe it in three parts. Using blue sapphire as an example, here is how each one changes the look of a stone.
Hue
The basic colour family. The finest sapphires sit at pure blue to slightly violetish blue.
Tone
How light or dark the colour appears. Medium to medium-dark tones are the most desirable.
Saturation
The strength or purity of the colour. The more vivid, the more valuable the gem.
How Coloured Gems Are Cut
Unlike diamonds, coloured gemstones are cut first for colour, then for weight and sparkle. Transparent stones are usually faceted; opaque or phenomenal stones — opal, moonstone, turquoise — are polished as smooth, domed cabochons. Seen from the side, proportions reveal a lot about quality.
Faceted (mixed cut)
Well proportionedA brilliant-style crown over a step-cut pavilion — the most common cut for ruby, sapphire and spinel, balancing colour and sparkle.
Cabochon
For opaque & phenomenal gemsA smooth dome with a flat or slightly curved base. Ideal for showing play-of-colour, sheen or star effects.
Too shallow
Colour is lostLight passes straight through the base, leaving a pale, washed-out “window” in the centre.
Too deep
Stone looks darkExcess weight in the pavilion creates dark, lifeless areas known as extinction.
Clarity Types for Coloured Gems
Coloured gemstones are not graded on the diamond clarity scale. Instead, each variety is placed in one of three types according to how included it typically is in nature — so a lightly included emerald can be exceptional, while the same inclusions in an aquamarine would not be.
Type I
Usually eye-cleanGrow in nature with very few inclusions. Visible inclusions noticeably reduce value.
Aquamarine · Morganite · Tanzanite · Topaz · Green tourmaline
Type II
Usually includedNormally contain some inclusions; eye-clean stones are valued highly.
Ruby · Sapphire · Spinel · Alexandrite · Garnet · Amethyst · Citrine · Peridot · Most tourmaline
Type III
Almost always includedInclusions are part of their character; eye-clean stones are extremely rare.
Emerald · Red and watermelon tourmaline
Clarity types follow the classification used by leading gemmological laboratories. Opal, moonstone, pearl and turquoise are judged on other qualities, such as play-of-colour, sheen or lustre.
The Hardness Chart
The Mohs scale ranks resistance to scratching from 1 to 10. Everyday dust contains quartz (7), so gems below 7 can gradually lose their polish. Harder stones are best for rings worn daily; softer gems shine in earrings and pendants.
18 Gemstones at a Glance
The colours each gem is found in, what the most prized stones look like, and how to choose and care for them.
Ruby
Pinkish red, Red, Slightly purplish red, Dark red
Most prized: Pure, vivid red to slightly purplish red — neither too light nor too dark.
- Clarity
- Type II · inclusions are expected; eye-clean stones are rare
- Best cuts
- Oval, cushion
- Birthstone
- July
- Treatments
- Heating is common
- Daily rings
- Excellent
Warm soapy water. Avoid ultrasonic for glass-filled stones.
Sapphire
Royal blue, Cornflower, Pink, Padparadscha, Yellow, Purple, Green, White
Most prized: Velvety blue to violetish blue in medium to medium-dark tones; also found in almost every other colour.
- Clarity
- Type II · blue sapphires often show some inclusions
- Best cuts
- Oval, cushion, round
- Birthstone
- September
- Treatments
- Heating is common and accepted
- Daily rings
- Excellent
Warm soapy water; ultrasonic usually safe for untreated or heated stones.
Emerald
Bluish green, Green, Yellowish green, Deep green
Most prized: Bluish green to pure green with vivid saturation, not too dark.
- Clarity
- Type III · almost always included — the famous “jardin”
- Best cuts
- Emerald cut (follows the crystal shape)
- Birthstone
- May
- Treatments
- Oiling or resin filling is routine
- Daily rings
- With care
Warm soapy water and a soft brush only. Never ultrasonic or steam.
Spinel
Red, Hot pink, Orange, Lavender, Cobalt blue, Grey
Most prized: Intense reds, vivid pinks and rare cobalt blues, with no visible inclusions.
- Clarity
- Type II · clean stones are preferred
- Best cuts
- Cushion, oval
- Birthstone
- August
- Treatments
- Rarely treated
- Daily rings
- Excellent
Warm soapy water; ultrasonic usually safe.
Alexandrite
Daylight: bluish green, Incandescent: purplish red
Most prized: A strong, clean colour change — green in daylight, red to purplish red under warm light.
- Clarity
- Type II · usually included
- Best cuts
- Cushion, oval
- Birthstone
- June
- Treatments
- Rarely treated
- Daily rings
- Excellent
Warm soapy water; ultrasonic usually safe.
Tanzanite
Blue, Violetish blue, Purple
Most prized: Rich violetish blue to blue; shows different hues from different angles (pleochroism).
- Clarity
- Type I · usually eye-clean
- Best cuts
- Cushion, oval, trillion
- Birthstone
- December
- Treatments
- Heating is standard
- Daily rings
- Protective setting
Warm soapy water. Avoid ultrasonic, steam and hard knocks.
Aquamarine
Pale blue, Sea blue, Deep blue, Greenish blue
Most prized: Moderately strong, pure blue to slightly greenish blue.
- Clarity
- Type I · usually eye-clean
- Best cuts
- Emerald cut, oval
- Birthstone
- March
- Treatments
- Heating to remove green tints is common
- Daily rings
- Very good
Warm soapy water; ultrasonic usually safe for stones without fractures.
Morganite
Pink, Peach, Salmon
Most prized: Clean, saturated pink to peachy pink.
- Clarity
- Type I · usually eye-clean
- Best cuts
- Oval, cushion, round
- Birthstone
- —
- Treatments
- Often heated to enhance pink
- Daily rings
- Very good
Warm soapy water; ultrasonic usually safe.
Tourmaline
Pink, Red (rubellite), Green, Blue (indicolite), Neon blue-green, Watermelon
Most prized: Almost every colour imaginable — vivid, neon blue-green stones are among the most sought after.
- Clarity
- Type I (green) · Type II (most colours) · Type III (red, watermelon)
- Best cuts
- Emerald cut, oval, cushion
- Birthstone
- October
- Treatments
- Heating or irradiation may be used
- Daily rings
- Very good
Warm soapy water. Ultrasonic and steam are not recommended.
Garnet
Deep red, Rhodolite, Spessartine orange, Tsavorite green, Demantoid
Most prized: Clean, saturated colour — from wine red to vivid orange and bright green.
- Clarity
- Type II · usually included
- Best cuts
- Round, oval, cushion
- Birthstone
- January
- Treatments
- Rarely treated
- Daily rings
- Good
Warm soapy water; ultrasonic usually safe except for demantoid.
Amethyst
Lilac, Purple, Deep violet
Most prized: Deep reddish purple to purple, without brown or grey tones.
- Clarity
- Type II · often eye-clean in commercial sizes
- Best cuts
- Oval, cushion, round
- Birthstone
- February
- Treatments
- Heating is common
- Daily rings
- Good
Warm soapy water; keep away from strong heat and prolonged strong light.
Citrine
Pale yellow, Golden, Madeira orange
Most prized: Saturated golden yellow to reddish orange, free of brownish tones.
- Clarity
- Type II · often eye-clean
- Best cuts
- Cushion, oval, round
- Birthstone
- November
- Treatments
- Most citrine is heat-treated amethyst
- Daily rings
- Good
Warm soapy water; ultrasonic usually safe.
Peridot
Yellowish green, Lime green, Olive green
Most prized: Pure green with only a slight yellow tint.
- Clarity
- Type II · usually included
- Best cuts
- Oval, cushion, round
- Birthstone
- August
- Treatments
- Rarely treated
- Daily rings
- Protective setting
Warm soapy water. Avoid ultrasonic, steam, acids and sudden heat.
Topaz
Imperial golden orange, Pink, Sky blue, London blue, Colourless
Most prized: Vivid golden orange to pinkish orange (“imperial”), and rich pinks.
- Clarity
- Type I · usually eye-clean
- Best cuts
- Pear, oval, cushion
- Birthstone
- November
- Treatments
- Blue topaz is usually irradiated and heated
- Daily rings
- With care
Warm soapy water. Avoid ultrasonic and steam — topaz can split along its cleavage.
Opal
White opal, Black opal, Fire opal, Boulder opal
Most prized: Bright, broad flashes of play-of-colour across the whole stone; reds are the rarest.
- Clarity
- Judged on play-of-colour, pattern and body tone
- Best cuts
- Cabochon
- Birthstone
- October
- Treatments
- May be stabilised or assembled (doublets, triplets)
- Daily rings
- Occasional wear
Wipe with a soft damp cloth. Avoid ultrasonic, steam, heat and sudden temperature changes.
Moonstone
Colourless, Peach, Grey, Rainbow
Most prized: A transparent body with a bright blue, floating sheen (adularescence).
- Clarity
- Judged on transparency and sheen
- Best cuts
- Cabochon
- Birthstone
- June
- Treatments
- Rarely treated
- Daily rings
- Occasional wear
Warm soapy water. Avoid ultrasonic and steam.
Pearl
White, Cream, Rosé, Silver, Golden, Tahitian black
Most prized: Sharp, mirror-like lustre, a clean surface and even nacre.
- Clarity
- Judged on lustre, surface, shape, colour, size and nacre
- Best cuts
- Round, near-round, baroque
- Birthstone
- June
- Treatments
- Sometimes bleached or dyed
- Daily rings
- Occasional wear
Wipe with a soft cloth after wearing. Never soak. Last on, first off.
Turquoise
Sky blue, Greenish blue, Green, With matrix
Most prized: An even, intense sky blue, with or without a fine spider-web matrix.
- Clarity
- Opaque · judged on colour, matrix and texture
- Best cuts
- Cabochon
- Birthstone
- December
- Treatments
- Often stabilised
- Daily rings
- Occasional wear
Wipe with a dry or damp cloth only — turquoise is porous.
Gemstone Comparison Table
| Gemstone | Species | Colours | Mohs | Clarity | Birthstone | Ultrasonic |
|---|---|---|---|---|---|---|
| Diamond | Carbon | 10 | FL – I3 scale | April | Usually safe | |
| Ruby | Corundum | 9 | Type II | July | Use care | |
| Sapphire | Corundum | 9 | Type II | September | Usually safe | |
| Emerald | Beryl | 7.5–8 | Type III | May | Avoid | |
| Spinel | Spinel | 8 | Type II | August | Usually safe | |
| Alexandrite | Chrysoberyl | 8.5 | Type II | June | Usually safe | |
| Tanzanite | Zoisite | 6–7 | Type I | December | Avoid | |
| Aquamarine | Beryl | 7.5–8 | Type I | March | Usually safe | |
| Morganite | Beryl | 7.5–8 | Type I | — | Usually safe | |
| Tourmaline | Tourmaline group | 7–7.5 | Type I–III | October | Avoid | |
| Garnet | Garnet group | 6.5–7.5 | Type II | January | Use care | |
| Amethyst | Quartz | 7 | Type II | February | Use care | |
| Citrine | Quartz | 7 | Type II | November | Usually safe | |
| Peridot | Olivine (forsterite) | 6.5–7 | Type II | August | Avoid | |
| Topaz | Topaz | 8 | Type I | November | Avoid | |
| Opal | Opal (hydrated silica) | 5.5–6.5 | Judged on play-of-colour, pattern and body tone | October | Avoid | |
| Moonstone | Feldspar | 6–6.5 | Judged on transparency and sheen | June | Avoid | |
| Pearl | Organic (nacre) | 2.5–4.5 | Judged on lustre, surface, shape, colour, size and nacre | June | Avoid | |
| Turquoise | Turquoise | 5–6 | Opaque | December | Avoid |
Care guidance is general. Treated, filled or fractured stones may need extra care — when in doubt, clean with warm soapy water and a soft brush, or bring your jewellery to us.
Find the gemstone that feels like you
Book a private consultation to see sapphires, rubies, emeralds and rare gems side by side — or let us design a bespoke piece around a birthstone or a family stone.
Book a consultationView the diamond chartIllustrations and colour swatches are representative only; natural gemstones vary and screen colours differ.
