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Rocks & minerals

What gemstone is this?

Colour alone identifies almost nothing — ruby, red spinel, garnet and glass all look the same across a room, and for two hundred years the most famous "ruby" in the British crown jewels was a spinel. Filter by colour plus hardness plus any optical effect, and check the look-alike line on every entry, because for gemstones the imitation is usually the answer.

Entries 27Filters 5 Updated 2026-09-04 Cost Free, no account

Narrow it down

Colour
Hardness

Test on an unpolished spot such as the girdle, never a facet.

Transparency
Optical effect
Category

Showing all 27 gemstones

  1. Diamond

    C — carbon

    Extreme brilliance and hard, sharply defined facet edges that stay crisp because nothing abrades them. Singly refractive, so facet edges seen through the table are single, not doubled.

    Size
    Mohs 10; refractive index 2.42
    Where
    Kimberlite pipes in southern Africa, Russia, Canada and Australia.
    Confused with
    Moissanite doubles the facet edges under magnification. Cubic zirconia is denser and has lower thermal conductivity, which is what a jeweller's pen tester measures. The old "scratches glass" test proves nothing — all three do.

    In the record Mohs 10 · C · isometric · adamantine lustre check on Macrostrat

  2. Ruby

    Corundum, Al₂O₃

    Red corundum, from pinkish to deep pigeon's blood, with a strong red fluorescence under ultraviolet light in Burmese material. Star rubies show a six-rayed star from oriented rutile needles.

    Size
    Mohs 9
    Where
    Myanmar, Mozambique, Thailand, Madagascar.
    Confused with
    Red spinel, which is softer at 8 and singly refractive; garnet, which is softer still; and glass. The Black Prince's Ruby in the Imperial State Crown is a spinel.

    In the record Mohs 9 · Al2O3 · trigonal · adamantine lustre check on Macrostrat

  3. Sapphire

    Corundum, Al₂O₃

    Corundum in any colour except red, so there are yellow, pink, green and colourless sapphires as well as blue. Very hard, with a slightly oily lustre and often visible straight colour banding.

    Size
    Mohs 9
    Where
    Sri Lanka, Madagascar, Kashmir, Montana, Australia.
    Confused with
    Tanzanite, which is much softer at 6 to 7 and shows different colours from different directions. Blue glass and synthetic sapphire are both common; synthetic material is chemically identical and needs a lab to detect.

    In the record Mohs 9 · Al2O3 · trigonal · adamantine lustre check on Macrostrat

  4. Emerald

    Handle with care

    Beryl, Be₃Al₂Si₆O₁₈

    Deep green beryl, almost always heavily included — the internal fractures and crystals are called the jardin, the garden, and their absence in a clean stone is a warning rather than a virtue.

    Size
    Mohs 7.5–8
    Where
    Colombia, Zambia, Brazil, Afghanistan.
    Confused with
    Green glass, synthetic emerald, and doublets glued from two pieces with green cement. Most natural emerald is oil- or resin-treated to fill the fractures, which is normal and disclosed but affects durability and cleaning.
    Risk
    Never clean an emerald ultrasonically or with steam. It strips the filling and can crack the stone along an existing fracture.

    In the record Mohs 7.5–8 · Be3Al2(Si6O18) · hexagonal · vitreous lustre check on Macrostrat

  5. Aquamarine

    Beryl, Be₃Al₂Si₆O₁₈

    Pale sea-blue to blue-green beryl, typically very clean, in large flawless crystals. Colour is usually pale in natural stones; a deep blue aquamarine has almost always been heat-treated.

    Size
    Mohs 7.5–8
    Where
    Brazil, Pakistan, Nigeria, Madagascar.
    Confused with
    Blue topaz, which is denser and heavier for its size, and blue glass, which contains bubbles.

    In the record Mohs 7.5–8 · Be3Al2(Si6O18) · hexagonal · vitreous lustre check on Macrostrat

  6. Amethyst

    Quartz, SiO₂

    Purple quartz, often with visible colour zoning in angular bands or a paler zone towards the crystal base. Sold in geodes and clusters everywhere.

    Size
    Mohs 7
    Where
    Brazil, Uruguay, Zambia, Russia.
    Confused with
    Purple glass and synthetic amethyst, which is chemically identical and cheap. Deep colour fades in prolonged sunlight, which is real and irreversible.

    In the record Mohs 7 · SiO2 · trigonal · vitreous lustre check on Macrostrat

  7. Citrine

    Quartz, SiO₂

    Yellow to orange-brown quartz. Natural citrine is a pale lemon; almost every deep orange-brown "citrine" on the market is heat-treated amethyst, which is legitimate and should be disclosed.

    Size
    Mohs 7
    Where
    Brazil, Bolivia, Madagascar.

    In the record Mohs 7 · SiO2 · trigonal · vitreous lustre check on Macrostrat

  8. Topaz

    Handle with care

    Al₂SiO₄(F,OH)₂

    Hard, bright and noticeably heavy for its size, with a slippery slightly soapy feel. Almost all blue topaz on the market is irradiated and heated colourless material.

    Size
    Mohs 8
    Where
    Brazil, Nigeria, Pakistan, Russia.
    Risk
    Perfect basal cleavage. Topaz resists scratching beautifully and splits from a single sharp knock, so it needs a protective setting in a ring.

    In the record Mohs 8 · Al2(SiO4)(F,OH)2 · orthorhombic · vitreous lustre check on Macrostrat

  9. Garnet

    X₃Y₂(SiO₄)₃ group

    A whole family rather than one stone. Deep red almandine is the familiar one; there are also orange spessartine, green tsavorite, brilliant green demantoid and colour-change species. Singly refractive with no cleavage.

    Size
    Mohs 6.5–7.5
    Where
    Worldwide; almandine in schist, demantoid in Russia, tsavorite in Kenya.
    Confused with
    Ruby, which is much harder and fluoresces red. Garnet is denser than most red stones and sinks fast in heavy liquids, which is how gemmologists separate them.

    In the record Mohs 6.5–7.5 · X3Z2(SiO4)3 · isometric · vitreous to resinous lustre check on Macrostrat

  10. Peridot

    Olivine, (Mg,Fe)₂SiO₄

    A distinctive oily olive-green with a yellow undertone, and strong double refraction — look through the table with a loupe and the back facet edges appear doubled.

    Size
    Mohs 6.5–7
    Where
    Arizona, Pakistan, Myanmar, and in meteorites.
    Confused with
    Emerald and green glass. The doubled facet edges are diagnostic and easy to see.

    In the record Mohs 6.5–7 · (Mg,Fe2+)2SiO4 · orthorhombic · vitreous lustre check on Macrostrat

  11. Tourmaline

    Complex borosilicate

    Comes in more colours than any other gem species, often several in one crystal — watermelon tourmaline is pink-cored and green-rimmed. Rough crystals have a rounded-triangular cross-section with heavy lengthwise striations.

    Size
    Mohs 7–7.5
    Where
    Brazil, Afghanistan, Nigeria, Maine, California.

    In the record Mohs 7 · A(D3)G6(T6O18)(BO3)3X3Z · trigonal check on Macrostrat

  12. Spinel

    MgAl₂O₄

    Bright, singly refractive and often in octahedral crystals. Historically sold as ruby, and now increasingly valued in its own right for the vivid red and the cobalt blue.

    Size
    Mohs 8
    Where
    Myanmar, Tanzania, Sri Lanka, Vietnam.
    Confused with
    Ruby. Spinel is singly refractive and ruby is doubly refractive — a polariscope or a loupe check for doubled facet edges settles it in seconds.

    In the record Mohs 7.5–8 · MgAl2O4 · isometric · vitreous lustre check on Macrostrat

  13. Tanzanite

    Handle with care

    Zoisite, Ca₂Al₃(SiO₄)₃(OH)

    Violet-blue with strong pleochroism — it shows blue, violet and burgundy from three different directions, which is visible by rotating the stone in the hand. Nearly all material is heat-treated to remove the brown.

    Size
    Mohs 6–7
    Where
    One hill in Tanzania and nowhere else on Earth.
    Risk
    Soft, with distinct cleavage and sensitivity to sudden temperature change. A poor choice for an everyday ring and unsuited to ultrasonic cleaning.

    In the record Mohs 6–7 · {Ca2}{Al3}(Si2O7)(SiO4)O(OH) · orthorhombic · vitreous lustre check on Macrostrat

  14. Opal

    Handle with care

    SiO₂·nH₂O

    Flashes of spectral colour that move as the stone moves — play of colour, produced by diffraction from a regular array of silica spheres. This is not the same as an overall body colour.

    Size
    Mohs 5.5–6.5
    Where
    Australia, Ethiopia, Mexico, Brazil.
    Confused with
    Doublets and triplets, thin slices of opal backed with dark material and capped with quartz or glass. Look at the stone from the side: a straight-line junction means an assembled stone.
    Risk
    Contains up to 20% water and crazes into a network of fine cracks if dried by heat or low humidity. Never ultrasonic, never steam, never leave in a hot car.

    In the record Mohs 5.5–6.5 · SiO2·nH2O · vitreous lustre check on Macrostrat

  15. Moonstone

    Orthoclase feldspar

    A soft blue or white glow that floats across the surface and moves as you tilt the stone — adularescence, caused by light scattering between microscopic layers of two feldspars.

    Size
    Mohs 6–6.5
    Where
    Sri Lanka, India, Madagascar.
    Confused with
    Opalite, a manufactured glass sold widely as moonstone, which contains bubbles and has a flat orange glow in transmitted light.

  16. Labradorite

    Plagioclase feldspar

    Dull grey until the angle is right, then a broad flash of peacock blue, green or gold across the whole surface — labradorescence, from light interference in internal lamellae.

    Size
    Mohs 6–6.5
    Where
    Labrador, Finland, Madagascar.

    In the record Mohs 6–6.5 · (Ca,Na)[Al(Al,Si)Si2O8] · sub-vitreous lustre check on Macrostrat

  17. Turquoise

    CuAl₆(PO₄)₄(OH)₈·4H₂O

    Opaque sky-blue to green, usually with a web of dark host rock called matrix. Porous, so it absorbs oils and changes colour over years of wear.

    Size
    Mohs 5–6
    Where
    Iran, the US Southwest, China.
    Confused with
    Dyed howlite and magnesite, which are extremely common and can be detected by rubbing an inconspicuous spot with acetone — the dye lifts. Most commercial turquoise is stabilised with resin, which is standard practice.

    In the record Mohs 5–6 · Cu(Al,Fe3+)6(PO4)4(OH)8·4H2O · triclinic · sub-vitreous lustre check on Macrostrat

  18. Lapis lazuli

    Lazurite in a rock matrix

    Deep ultramarine blue flecked with brassy specks of pyrite and often white streaks of calcite. It is a rock rather than a mineral, which is why the composition varies.

    Size
    Mohs 5–6
    Where
    Afghanistan, principally the Sar-e-Sang mines, for over 6,000 years.
    Confused with
    Dyed jasper sold as lapis, which is uniformly blue with no pyrite. Ground lapis was the source of ultramarine pigment and was once worth more than gold.

  19. Jade — jadeite and nephrite

    NaAlSi₂O₆ / Ca₂(Mg,Fe)₅Si₈O₂₂(OH)₂

    Two different minerals sold under one name. Both are made of densely interlocked fibrous crystals, which makes jade extraordinarily tough — resistant to breaking rather than to scratching — and gives it a slightly greasy lustre and a solid ring when tapped.

    Size
    Mohs 6–7
    Where
    Jadeite from Myanmar; nephrite from China, British Columbia, New Zealand.
    Confused with
    Serpentine, aventurine quartz and dyed quartzite are all sold as jade. Dyed jadeite, called B-jade, is bleached and resin-impregnated and degrades over years.

  20. Agate, jasper and carnelian

    Chalcedony, SiO₂

    Microcrystalline quartz. Agate is banded and translucent, jasper is opaque and patterned, carnelian is translucent orange-red. All are hard enough to scratch glass and all take a high polish.

    Size
    Mohs 6.5–7
    Where
    Worldwide; abundant in Brazil, Uruguay, Oregon and Montana.
    Confused with
    Dyed agate is everywhere — the vivid blue, purple and green slices sold as bookends and coasters are dyed, and the colour is often obvious in the unnaturally even bands.

  21. Amber

    Fossilised tree resin

    Warm to the touch, very light — it floats in saturated salt water — and it takes a static charge when rubbed, picking up small pieces of paper. Often contains insects or plant fragments.

    Size
    Mohs 2–2.5
    Where
    The Baltic coast, the Dominican Republic, Myanmar.
    Confused with
    Copal, which is young resin and dissolves in acetone, and plastic, which sinks in salt water and smells of burning plastic under a hot pin rather than of pine.

  22. Pearl

    Handle with care

    Nacre — aragonite and conchiolin

    The tooth test: draw a pearl gently along the biting edge of a front tooth. A real pearl feels distinctly gritty from the microscopic aragonite platelets; an imitation feels perfectly smooth.

    Size
    Mohs 2.5–4.5
    Where
    Cultured in Japan, China, Australia and French Polynesia.
    Risk
    Soft, porous and destroyed by perfume, hairspray, vinegar and even sweat. Put pearls on last and wipe them after wearing.

  23. Alexandrite

    Chrysoberyl, BeAl₂O₄

    Green in daylight and red under incandescent light, because its absorption spectrum happens to sit exactly between the two illuminants. Genuine strong-change material is one of the rarest and most valuable gems there is.

    Size
    Mohs 8.5
    Where
    Originally the Urals; now Brazil, Sri Lanka, East Africa.
    Confused with
    Colour-change synthetic corundum and synthetic alexandrite are both common. Most "alexandrite" sold cheaply is one of these.

    In the record Mohs 8.5 · BeAl2O4 · orthorhombic · vitreous lustre check on Macrostrat

  24. Zircon

    ZrSiO₄

    Very high dispersion and extremely strong double refraction — the doubling of the back facet edges is obvious under a loupe. Heavy for its size.

    Size
    Mohs 6–7.5
    Where
    Cambodia, Sri Lanka, Australia.
    Confused with
    Entirely unrelated to cubic zirconia despite the name. Zircon is a natural mineral, and the oldest known terrestrial material is a zircon crystal 4.4 billion years old.

    In the record Mohs 7.5 · Zr(SiO4) · tetragonal · adamantine lustre check on Macrostrat

  25. Moissanite

    SiC — silicon carbide

    Very close to diamond in hardness and brilliance, but strongly doubly refractive — look through the table with a loupe and the opposite facet edges are visibly doubled. Dispersion is higher, giving more coloured fire.

    Size
    Mohs 9.25
    Where
    Almost all material is laboratory-grown.
    Confused with
    Sold both honestly as a diamond alternative and dishonestly as diamond. Old thermal-probe testers read it as diamond; modern combined thermal and electrical testers do not.

    In the record Mohs 9.5 · SiC · hexagonal · vitreous lustre check on Macrostrat

  26. Cubic zirconia

    ZrO₂

    Denser than diamond, so a CZ of the same apparent size is noticeably heavier. Facet edges soften with wear because it is softer, and older stones look cloudy where a diamond would still be crisp.

    Size
    Mohs 8–8.5
    Where
    Entirely laboratory-grown since the 1970s.

    In the record Mohs 8 · ZrO2 · isometric · sub-adamantine lustre check on Macrostrat

  27. Glass and paste

    Amorphous silica with additives

    Rounded rather than crisp facet edges from moulding, gas bubbles visible under a loupe, swirl marks, and warmth — glass reaches skin temperature faster than any crystalline gem. Softer than quartz, so a quartz point scratches it.

    Size
    Mohs 5–6
    Where
    Everywhere, in every colour.
    Confused with
    Imitates every gem on this list. The bubble check under 10× magnification catches most of it.

Four tests you can do with no equipment

Professional gem identification uses a refractometer, a polariscope, a spectroscope and a specific-gravity balance. Without any of those, four checks still eliminate most imitations.

  1. Look for gas bubbles under 10× magnification. Round bubbles mean glass or a plastic. Natural stones contain crystals, fractures and needles, but not spherical bubbles. A cheap loupe is the single most useful gemmological purchase there is.
  2. Check for doubling. Look through the table at the back facet edges with a loupe. If they appear doubled, the stone is strongly doubly refractive — peridot, zircon, moissanite, tourmaline. Diamond, spinel, garnet and glass never double.
  3. Feel the temperature. Glass and plastic warm to skin temperature quickly; crystalline gems stay cool because they conduct heat away. Amber is the exception among naturals — it feels warm, and that is diagnostic against glass, which feels cool by comparison.
  4. Heft it. Density varies enormously and the hand is surprisingly good at it. Cubic zirconia is heavier than diamond, topaz is heavier than quartz, and garnet is heavier than almost anything else red.

The one test to skip is scratching. It damages the stone, it is unreliable on a faceted gem, and the popular version of it — scratching glass — separates nothing, because everything from quartz upwards does it.

Optical effects, and what causes each

Several gems are identified by a phenomenon rather than by colour, and each has a specific mechanism.

Optical phenomena in gemstones and the structures that produce them.
EffectWhat you seeCauseTypical gems
Play of colourFlashes of spectral colour that shift as the stone movesDiffraction from a regular array of silica spheresOpal, and nothing else
AsterismA four- or six-rayed starReflection from oriented needle inclusionsStar ruby, star sapphire, star garnet
ChatoyancyA single bright band like a cat's eyeParallel fibrous inclusions or channelsChrysoberyl, tiger's eye, tourmaline
AdularescenceA soft glow that floats under the surfaceLight scattering between microscopic feldspar layersMoonstone
LabradorescenceA broad flash of peacock colour at one angleInterference in internal lamellaeLabradorite, spectrolite
Colour changeA different colour in daylight and lamplightAn absorption spectrum sitting between the two illuminantsAlexandrite, some garnet and sapphire
PleochroismDifferent colours from different directionsDirection-dependent absorption in the crystalTanzanite, iolite, andalusite

The distinction that trips people up is between play of colour and iridescence. Opal's flashes come from a regular internal structure and move independently of the surface; the rainbow on a soap bubble or an oil film is thin-film interference and is a surface effect. Only opal does the first.

Treated, synthetic, simulant: three different words

These are constantly used interchangeably and they mean quite different things commercially and legally.

Treated means a natural stone modified after mining — heated, irradiated, oiled, dyed or fracture-filled. Treatment is routine and mostly acceptable: essentially all blue topaz is irradiated, nearly all tanzanite is heated, and most emerald is oiled. It must be disclosed, and it affects both value and care instructions.

Synthetic means grown in a laboratory with the same chemical composition and crystal structure as the natural stone. A synthetic ruby is a ruby by every physical and chemical test, and separating it from a mined one requires a laboratory looking at growth features. It is a real gem, worth far less, and must be disclosed.

Simulant means a different material that looks like the gem. Cubic zirconia simulating diamond, glass simulating anything, dyed howlite simulating turquoise. These are cheap and identifiable with basic tests.

In the United States the Federal Trade Commission requires all three to be disclosed, and a stone described simply as "ruby" must be natural and untreated beyond normal practice. Where a seller is vague, assume treatment. Where a price is far below the market, assume synthetic or simulant.

Buying without getting caught

  • Above a few hundred, get a laboratory report. GIA, AGS, IGI and, in Europe, Gübelin and SSEF issue reports naming the species, origin where determinable, and every treatment detected. A seller unwilling to allow independent testing is telling you something.
  • Ask three specific questions: is it natural or laboratory-grown, what treatments has it had, and is the weight the total for the piece or for the main stone. Vague answers are the answer.
  • Be suspicious of perfect. Flawless emerald, uniformly perfect turquoise, and evenly coloured amber with a photogenic insect centred in it are all warnings. Natural material has character because it grew in the ground.
  • Treat "certified" as meaningless on its own. Certificates issued by the seller are marketing. The issuing laboratory is the whole content of the claim.
  • Do not buy loose stones on holiday. Gem scams targeting tourists are a well-established industry in several countries, and the recourse afterwards is nil.

Wearing and cleaning without damaging the stone

Hardness governs scratching, and three other properties govern everything else.

Cleavage. Topaz, tanzanite, fluorite and diamond all have cleavage planes and can split from a single well-placed knock regardless of hardness. This is why an 8-hardness topaz needs a protective setting in a ring.

Porosity. Turquoise, pearl, opal, coral and amber absorb liquids. Perfume, hairspray, cleaning products and sweat all damage them, and the rule is to put them on last and wipe them after wearing.

Heat and water sensitivity. Opal holds up to 20% water and crazes if it dries. Emerald is oil-filled. Pearl is a soft organic material. Never put opal, emerald, pearl, turquoise, amber, tanzanite or coral in an ultrasonic or steam cleaner. Warm water, mild soap and a soft brush is the right treatment for nearly everything.

Storage matters too: harder stones scratch softer ones in a shared box, so a diamond loose in a jewellery box will mark every other stone in it. Individual soft pouches solve it entirely.

27 entries here cover the gems and imitations that come up in practice. There are several thousand mineral species with gem-quality material, and any collection of unusual cut stones will contain things not on this list. For anything that matters financially, the answer is a laboratory report rather than a chart.

Hardness, formula and crystal system

Colour is the least reliable thing about a mineral and hardness is the most reliable, because hardness is a measurement rather than an impression. Every entry in this key that has a formal mineral name is matched against Macrostrat's mineral definitions, which gives 20 of the 27 entries a published Mohs range, a chemical formula, a crystal system and a lustre. The snapshot was taken on 2026-09-04.

Mohs hardness range of 20 gemstones, with everyday scratch-test references 1 2 3 4 5 6 7 8 9 10 fingernail copper coin steel knife quartz Turquoise Opal Labradorite Tanzanite Peridot Amethyst Citrine Garnet Tourmaline Zircon Emerald Aquamarine Spinel Topaz Cubic zirconia Alexandrite Ruby Sapphire Moissanite Diamond Mohs hardness — the dashed lines are what you already have in a pocket
Published Mohs ranges for the 20 gemstones in this key, softest at the top. A steel knife blade sits at about 5.5, and it splits the list almost in half: 0 of 20 can be scratched by one, the rest cannot. Turquoise is the softest here and Diamond the hardest. Source: Macrostrat mineral definitions, CC BY 4.0, snapshot 2026-09-04.

Read that figure as a sequence of tests rather than a list of facts. A fingernail is about 2.5 on the Mohs scale and will mark 0 of these 20. A steel knife blade is about 5.5 and splits the rest: 0 can be scratched by one and the remainder cannot, which is a single test that removes most of the list. A piece of quartz at 7 will scratch everything below it. Do the test on a fresh surface and on the specimen rather than the crust, and scratch the mineral with the tool — a streak of metal left on the rock looks like a scratch and is not one. Crystal system is the other free character: 5 of these are trigonal, so the habit you can see in a good specimen narrows the field before any test at all.

The reference table

Formula, hardness range, crystal system and lustre for every named mineral in this key, as published. Where a hardness is given as a range, the mineral genuinely varies — usually with the direction of the scratch or the exact composition.

Published mineral properties for the 20 named entries in this key. Source: Macrostrat mineral definitions, CC BY 4.0, snapshot 2026-09-04. Free to reuse with a link to this page.
EntryFormulaMohsCrystal systemLustre
TurquoiseCu(Al,Fe3+)6(PO4)4(OH)8 · 4H25–6TriclinicSub-Vitreous, Resinous, Waxy, Dull, Earthy
OpalSiO2 · nH2O5.5–6.5—Vitreous, Waxy, Greasy, Dull
Tanzanite{Ca2}{Al3}(Si2O7)(SiO4)O(OH)6–7OrthorhombicVitreous
Labradorite(Ca,Na)[Al(Al,Si)Si2O8]6–6.5—Sub-Vitreous
GarnetX3Z2(SiO4)3 6.5–7.5Isometricvitreous to resinous
Peridot(Mg,Fe2+)2SiO46.5–7OrthorhombicVitreous
AmethystSiO27TrigonalVitreous
CitrineSiO27TrigonalVitreous
TourmalineA(D3)G6(T6O18)(BO3)3X7Trigonal—
EmeraldBe3Al2(Si6O18)7.5–8HexagonalVitreous, Sub-Vitreous, Waxy, Greasy
AquamarineBe3Al2(Si6O18)7.5–8HexagonalVitreous, Sub-Vitreous, Waxy, Greasy
SpinelMgAl2O47.5–8IsometricVitreous
ZirconZr(SiO4)7.5TetragonalAdamantine, Vitreous, Greasy
TopazAl2(SiO4)(F,OH)28OrthorhombicVitreous
Cubic zirconiaZrO28IsometricSub-Adamantine
AlexandriteBeAl2O48.5OrthorhombicVitreous
RubyAl2O39TrigonalAdamantine, Vitreous, Pearly
SapphireAl2O39TrigonalAdamantine, Vitreous, Pearly
MoissaniteSiC9.5HexagonalVitreous
DiamondC10IsometricAdamantine, Greasy

Free to reuse with a link back to this page. The full snapshot behind every Orvik key is on the open field data page.

Questions people ask about this

How can I tell if a gemstone is real?

A 10× loupe answers most of it. Round gas bubbles mean glass or plastic — natural stones contain crystals, needles and fractures but not spheres. Look through the table at the back facet edges: doubling means peridot, zircon, moissanite or tourmaline. Feel the temperature, since glass warms quickly while crystalline gems stay cool. And weigh it in the hand, because density varies enormously. Anything valuable needs a laboratory report.

Does scratching glass prove a stone is a diamond?

No. Glass is only about 5.5 on the Mohs scale, so quartz, topaz, garnet, sapphire, moissanite and cubic zirconia all scratch it easily. The test rules things out rather than in. Separating diamond from moissanite needs a check for doubled facet edges or a modern combined thermal and electrical tester; the old thermal-only probes read moissanite as diamond.

What is the difference between synthetic and simulant?

A synthetic has the same chemical composition and crystal structure as the natural stone but was grown in a laboratory — a synthetic ruby is genuinely a ruby, and separating it from a mined one requires laboratory examination of growth features. A simulant is a different material that merely looks like the gem, such as cubic zirconia standing in for diamond or dyed howlite for turquoise. Both must be disclosed under US FTC rules.

Why does my emerald have so many inclusions?

Because emeralds grow that way, and the internal fractures and crystals even have a name — the jardin, or garden. A completely clean emerald is a warning sign rather than a virtue: it is likely synthetic or glass. Most natural emerald is oil- or resin-filled to reduce the visibility of fractures, which is normal, disclosed practice and the reason emeralds must never be cleaned ultrasonically.

How do I know if a pearl is real?

Draw it gently along the biting edge of a front tooth. A real pearl feels distinctly gritty because of the microscopic aragonite platelets that make up nacre; an imitation feels perfectly smooth. Real pearls also feel cool at first touch and rarely match each other exactly in a strand. The test does not distinguish natural from cultured pearls, which needs X-ray imaging.

Which gemstones can I not put in an ultrasonic cleaner?

Opal, emerald, pearl, turquoise, amber, coral, tanzanite, and anything with visible fractures or a dyed or filled treatment. Ultrasonic and steam cleaning drive filling material out, dry porous stones, and can crack a stone along an existing fracture. Warm water, mild soap and a soft brush handle almost everything safely.

Is my turquoise real?

Much of the turquoise on the market is dyed howlite or magnesite, which are white minerals with a similar matrix pattern. Rub an inconspicuous spot with a cotton bud and a little acetone; dye lifts onto the swab. Real turquoise is also porous and changes colour slowly over years of wear, and most commercial material is stabilised with resin, which is standard and should be disclosed.

Still not sure? Point a camera at it

A filter narrows gemstones down to a shortlist. Orvik reads the photo itself and names the species, with the look-alikes ranked underneath so you can check the call yourself.

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