Interactive guide to gemstone hardness and colours for engagement rings and fine jewellery

Gemstone Hardness, Colour & Care — The Complete Guide

Fast answers for shoppers. Serious detail for gem lovers.

Durability = hardness (scratch resistance) + toughness (chip resistance) + stability (heat, chemicals, light). Mohs numbers help, but they’re only one part of the story.

Diamond

Mohs 10 · Excellent daily wear

Unmatched hardness with brilliant fire. Diamonds can still chip at thin points or along cleavage if struck.

D–F colourless
Icy white; top of the scale.
G–J near‑colourless
Great value; looks bright when set.
Fancy colours
Natural pink, blue, yellow—rare; intensity drives value.

Sapphire & Ruby (Corundum)

Mohs 9 · Excellent daily wear

Durable and versatile. Sapphires appear in blue, teal/parti, pink (incl. padparadscha), yellow, green and white. Heat treatment to enhance colour/clarity is common and should be disclosed.

Blue
Powder/cornflower → royal → midnight.
Teal & parti
Modern favourite; unique zoning and shifts.
Pink & padparadscha
Pink through vivid; padparadscha is pink‑orange and rare.
Yellow
Butter → canary; look for lively saturation.

Chrysoberyl & Alexandrite

Mohs 8.5 · Excellent daily wear

Alexandrite: bluish‑green in daylight, purplish‑red in incandescent light—nature’s colour‑change marvel. Cat’s‑eye chrysoberyl: sharp mobile band (chatoyancy) in cabochons.

Spinel

Mohs 8 · Excellent daily wear

Bright, clean and often untreated; colours from hot pink/red to cobalt, lavender and grey. Great all‑rounder.

Topaz

Mohs 8 · Excellent with care

Beautiful blues (Sky/Swiss/London) and prized golden “Imperial”. Note: perfect cleavage & fair toughness—avoid knocks; prefer protective settings; caution with ultrasonic/steam.

Beryl — Emerald · Aquamarine · Morganite

Mohs 7.5–8 · Good with protection

Emerald: vivid green, typically included; fractures often filled with oils/resins—treat gently. Aquamarine: clean sea‑blue, robust. Morganite: peach‑to‑blush pink, romantic.

Tourmaline

Mohs 7–7.5 · Good with protection

Rainbow palette: rubellite (red), hot pink, chrome/verdélite (green), indicolite (blue), and neon Paraíba (copper‑bearing).

Garnet Group

Mohs ~6.5–7.5 · Fair–good toughness

Beyond classic red: spessartite (orange), tsavorite (green), rhodolite (purplish), and demantoid (green, softer). Good everyday choice with care.

Quartz — Amethyst · Citrine · Ametrine

Mohs ~7 · Good with care

Vivid colours, budget‑friendly. Avoid hard knocks and abrupt heat changes; warm soapy water is safe.

Zircon (Natural, not CZ)

Mohs ~6–7.5 · Brittle; occasional wear

High brilliance; blue zircon is typically heat‑treated. Can abrade/chip—choose protective settings and mindful wear.

Tanzanite

Mohs ~6–7 · Softer; occasional wear

Violet‑blue pleochroic beauty; avoid shocks and heat; best in protective rings or as pendants/earrings for frequent wear.

Peridot

Mohs ~6.5–7 · Fair–good toughness

Sunny yellow‑green; wear with care to avoid scratches and sudden temperature swings.

Opal

Special care · Best in protective settings

Mesmerising play‑of‑colour but lower hardness/toughness. Clean only with warm, soapy water; avoid extremes of heat, chemicals and ultrasonics/steam.

Pearl

Organic gem · Gentle wear

Nacre thickness and continuity affect durability. Put pearls on last, take off first; wipe after wear; avoid perfumes, hairspray and acids.

Jade (Nephrite & Jadeite)

Moderate hardness · Exceptional toughness

Among the toughest gems thanks to interlocking crystal structures—historically used for tools. Great for bangles and carvings; still avoid harsh chemicals and hard shocks.

Organic Gemstones — Pearl · Amber · Coral · Shell

Formed by living organisms · Gentle wear

Organic gems form through biological processes rather than geological. They offer beauty and cultural significance, but generally have low hardness and require extra care.

Pearl

Mohs: ~2.5–4.5 · Toughness: fair (nacre layers can wear)

Valued for lustre and symbolism. Nacre thickness affects longevity. Care: Wipe after wear, store away from harder gems, avoid perfumes/acids, put on last and take off first.

Enhancements: bleaching, dyeing, coating.

Amber

Mohs: ~2–2.5 · Toughness: fair–poor

Fossilised tree resin, often with ancient inclusions. Very light, warm to touch. Care: Avoid solvents, alcohol, high heat, ultrasonic cleaning; store separately.

Enhancements: heat to improve clarity/colour, fracture filling.

Coral

Mohs: ~3–4 · Toughness: fair

Skeletons of marine organisms, valued for rich red, pink, white. Care: Avoid acids, heat, harsh cleaning; wipe with damp cloth and dry; store away from harder gems.

Enhancements: dyeing, wax/resin impregnation.

Shell (Mother‑of‑Pearl, Abalone)

Mohs: ~2.5–4.5 · Toughness: fair

Used for cameos, inlay, decorative pieces; valued for iridescence. Care: Wipe gently; avoid soaking, chemicals, and extremes.

Enhancements: bleaching, dyeing.

Best in pendants, earrings, or occasional‑wear rings with protective settings. Mindful wear extends heirloom life.

Diamond Simulants — Moissanite & Cubic Zirconia (CZ)

Moissanite ~9.25; CZ ~8–8.5

Moissanite (SiC): very hard, high RI & dispersion (more fire than diamond). CZ: budget sparkle; durable enough for jewellery but softer than corundum—expect more wear over time. Both are simulants (look like diamond, different materials).

Quick Care & Setting Tips

  • Everyday rings: Diamond; Sapphire/Ruby; Chrysoberyl/Alexandrite; Spinel.
  • Protective settings recommended: Emerald, Topaz, Zircon, Tanzanite, Peridot; Opal & Pearl (bezel/halo, low profile).
  • Ultrasonic caution: Avoid for fracture‑filled, oil‑treated, cleavage‑prone or heat‑sensitive gems (emerald, opal, topaz, tanzanite, zircon).
  • Cleaning baseline: Warm soapy water + soft brush. Dry thoroughly.

At‑a‑Glance Table (Hardness · Toughness · Notes)

Gem Mohs Toughness Everyday Ring? Notes
Diamond 10 Good (cleavage) Yes Can chip at points; D–Z colour scale.
Sapphire/Ruby (Corundum) 9 Good Yes Common heat treatment; many colours.
Chrysoberyl/Alexandrite 8.5 Good Yes Distinct colour change (Alexandrite).
Spinel 8 Good Yes Often untreated; vivid colours.
Topaz 8 Fair (cleavage) With care Protect from knocks; be careful cleaning.
Beryl (Emerald/Aqua/Morganite) 7.5–8 Fair–good With protection Emerald commonly oil/resin‑filled.
Tourmaline 7–7.5 Fair–good With protection Paraíba = copper‑bearing neon blue‑green.
Garnet (group) 6.5–7.5 Fair–good With care Wide palette (tsavorite, spessartite, etc.).
Quartz (Amethyst/Citrine) ~7 Good With care Avoid thermal shock; soapy water clean.
Zircon (natural) ~6–7.5 Fair Occasional Heat‑treated blue; brittle/abrades.
Tanzanite ~6–7 Fair Occasional Avoid shocks/ultrasonic; protective designs.
Peridot ~6.5–7 Fair–good With care Sensitive to rapid temp change.
Opal ~5.5–6.5 Fair–poor Occasional Only warm soapy water; avoid heat.
Pearl ~2.5–4.5 Fair (organic) Gentle Nacre thickness affects durability; avoid acids/heat; wipe after wear.
Amber ~2–2.5 Fair–poor Gentle Fossilised resin; avoid solvents/heat; store separately.
Coral ~3–4 Fair Gentle Organic CaCO₃; avoid acids/heat; store carefully.
Shell ~2.5–4.5 Fair Gentle Iridescent nacre; avoid soaking/chemicals.
Jade (Nephrite/Jadeite) ~6–7 Excellent Yes Exceptionally tough interlocking structure.
Moissanite ~9.25 Good Yes High fire; diamond simulant.
Cubic Zirconia (CZ) ~8–8.5 Fair–good With care Budget simulant; shows wear sooner.

General guidance only; individual stones vary by cut, inclusions and treatments.