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60 stones, one register.

Every stone in the encyclopedia with its species, hardness, refractive index, density and colors. Pick one to read its record.

Properties table Chapter 02 · The stones
Stones
60
Species
44
Properties
Mohs · RI · SG
Source
Chapter 02
(Fig. 01)Species sheet60 stones · 6 classes

A cadastre
of gem species.

Each parcel is one stone from the reference table, grouped with its family like plots in a land register. Select a parcel to read its record.

COL ACOL BCOL CCOL DCOL EROW 1ROW 2ROW 3JadeiteNephriteAlexandriteCitrineApatiteCarbonadoRose quartzDiamondRed berylPrecious opalSmoky quartzParaíba tourmalineCobalt blue spinelRed spinelLapis lazuliFancy sapphireBlue sapphireRubyTsavoriteSpessartinePadparadscha sapphireRubellitePearlPrecious coralAmberBenitoiteN
(Fig. 02)Stone pages31

One page per stone.

31 stones have their own page: properties, origins, care and the encyclopedia passages that discuss them.

(Fig. 03)Properties60 rows · sortable

The numbers
behind each stone.

Filter by family, search by name, sort by any column. Ranges show the spread a laboratory would accept for the species.

Fig. 02.1

Gem properties at a glance

60 rows

DiamondDiamondCcubic102.423.51–3.53colorless to yellow or brown; fancy colors
CarbonadoDiamondCcubic (polycrystalline)10–2.8–3.45black, opaque
RubyCorundumAl₂O₃trigonal91.762–1.773.95–4.05orangy red to purplish red
Blue sapphireCorundumAl₂O₃trigonal91.762–1.773.95–4.05light to dark blue
Padparadscha sapphireCorundumAl₂O₃trigonal91.762–1.773.95–4.05pinkish orange to orangy pink
Fancy sapphireCorundumAl₂O₃trigonal91.762–1.773.95–4.05violet, green, yellow, orange, pink, purple, parti-colored
EmeraldBerylBe₃Al₂Si₆O₁₈hexagonal7.5–81.577–1.5832.72green to bluish green
AquamarineBerylBe₃Al₂Si₆O₁₈hexagonal7.5–81.577–1.5832.72greenish blue, light in tone
MorganiteBerylBe₃Al₂Si₆O₁₈hexagonal7.5–81.583–1.592.8–2.91pink to orange-pink
Red berylBerylBe₃Al₂Si₆O₁₈hexagonal7.5–81.56–1.5722.65–2.72raspberry to purplish red
AlexandriteChrysoberylBeAl₂O₄orthorhombic8.51.746–1.7553.73bluish green in daylight, purplish red in incandescent light
PyropePyropeMg₃Al₂(SiO₄)₃cubic6.5–7.51.714–1.7423.582red, purplish red, orange-red
AlmandineAlmandineFe₃Al₂(SiO₄)₃cubic6.5–7.51.785–1.834.318deep red, brownish red, violet red
SpessartineSpessartineMn₃Al₂(SiO₄)₃cubic6.5–7.51.78–1.814.19light orange to reddish brown
TsavoriteGrossularCa₃Al₂(SiO₄)₃cubic71.739–1.7443.57–3.65light to intense green
HessoniteGrossularCa₃Al₂(SiO₄)₃cubic71.731–1.763.4–3.78orange to cinnamon brown
DemantoidAndraditeCa₃Fe₂(SiO₄)₃cubic6.51.88–1.8893.8–3.88yellowish green to green
RubelliteElbaiteNa(Li₁.₅,Al₁.₅)Al₆Si₆O₁₈(BO₃)₃(OH)₄trigonal7–7.51.624–1.6443–3.26pink, red, purplish red, orangy red, brownish red
IndicoliteElbaiteNa(Li₁.₅,Al₁.₅)Al₆Si₆O₁₈(BO₃)₃(OH)₄trigonal7–7.51.624–1.6443–3.26dark violetish blue, blue, greenish blue
Paraíba tourmalineElbaiteNa(Li₁.₅,Al₁.₅)Al₆Si₆O₁₈(BO₃)₃(OH)₄trigonal7–7.51.624–1.6443–3.26intense violetish blue, greenish blue, blue
Red spinelSpinelMgAl₂O₄cubic81.7183.6red to pink (chromium)
Cobalt blue spinelSpinelMgAl₂O₄cubic81.7183.6saturated blue (cobalt)
AmethystQuartzSiO₂trigonal71.544–1.5532.64–2.69light lilac to deep purple, often zoned
CitrineQuartzSiO₂trigonal71.544–1.5532.64–2.69yellow to orange to orangy red
Rose quartzQuartzSiO₂trigonal71.544–1.5532.64–2.69very light to medium-dark pink
Smoky quartzQuartzSiO₂trigonal71.544–1.5532.64–2.69light brown to black
AgateQuartz (chalcedony)SiO₂trigonal (microcrystalline)6.5–71.535–1.5392.6banded, many colors
ChrysopraseQuartz (chalcedony)SiO₂trigonal (microcrystalline)6.5–71.535–1.5392.6apple green
Precious opalOpalSiO₂·nH₂Oamorphous5–6.51.37–1.471.25–2.23white, gray or black body with play-of-color
JadeiteJadeiteNaAlSi₂O₆monoclinic (aggregate)6.5–71.666–1.683.34green, white, yellow, reddish orange, lavender, gray, black
NephriteActinolite-tremoliteCa₂(Mg,Fe)₅Si₈O₂₂(OH)₂monoclinic (aggregate)6–6.51.606–1.6322.95light to dark green, yellow, brown, black, gray, white
TanzaniteZoisiteCa₂Al₃(SiO₄)₃(OH)orthorhombic6–71.691–1.73.35violet blue to bluish violet to violet purple
TopazTopazAl₂SiO₄(F,OH)₂orthorhombic81.619–1.6273.53yellow, orange, brown, pink to red to purple, blue, colorless
ZirconZirconZrSiO₄tetragonal6–7.51.81–1.9843.9–4.73blue, red, yellow, orange, brown, green
PeridotOlivine(Mg,Fe)₂SiO₄orthorhombic6.5–71.65–1.693.34brown-green to yellowish green to pure green
IoliteCordieriteMg₂Al₄Si₅O₁₈orthorhombic7–7.51.542–1.5512.61violetish blue (pleochroic to colorless-yellow)
KunziteSpodumeneLiAlSi₂O₆monoclinic6.5–71.66–1.6763.18pink to violetish purple
TurquoiseTurquoiseCuAl₆(PO₄)₄(OH)₈·4H₂Otriclinic5–61.61–1.652.4–2.9blue to green
Lapis lazuliRock (lazurite, calcite, pyrite)Lazurite: Na₇Ca(Al₆Si₆O₂₄)(SO₄)(S₃)⁻·H₂Orock (lazurite cubic)5–61.5–1.672.5–3greenish blue to violetish blue, with calcite and pyrite
MalachiteMalachiteCu₂CO₃(OH)₂monoclinic3.5–4.51.655–1.9093.6–4.05light to dark green, banded
MoonstoneOrthoclaseKAlSi₃O₈monoclinic6–6.51.518–1.5262.58colorless to white, gray, green, peach, brown; blue sheen
LabradoritePlagioclase(Ca,Na)(Al,Si)₄O₈triclinic6–6.51.559–1.5682.7gray to dark with blue, green, gold flash
Sunstone (oligoclase)Plagioclase(Na,Ca)(Al,Si)₄O₈triclinic6–6.51.537–1.5472.65yellow, green, red, red-brown, colorless, with glitter
ApatiteApatiteCa₅(PO₄)₃(F,OH,Cl)hexagonal51.628–1.6493.1–3.35blue-green, green, yellow, violet, pink
SpheneTitaniteCaTiSiO₅monoclinic5–5.51.843–2.113.45–3.55yellow, green, brown
AndalusiteAndalusiteAl₂SiO₅orthorhombic6.5–7.51.627–1.6493.13–3.17green to reddish brown (pleochroic)
KyaniteKyaniteAl₂SiO₅triclinic5.5–71.71–1.7343.53–3.68blue, blue-green, green, orange
Chrome diopsideDiopsideCaMgSi₂O₆monoclinic5.5–6.51.664–1.733.22–3.38intense green
FluoriteFluoriteCaF₂cubic41.432–1.4343.18purple, green, blue, yellow, colorless
PainitePainiteCaZrAl₉O₁₅(BO₃)hexagonal7.5–81.787–1.8164.01red, brownish red, orange-red
TaaffeiteTaaffeiteBeMg₃Al₈O₁₆hexagonal8–8.51.716–1.7283.61–3.67mauve to purple, purplish red, grayish violet, colorless
GrandidieriteGrandidieriteMgAl₃BSiO₉orthorhombic7–7.51.583–1.6222.94–2.98greenish blue to blue-green
BenitoiteBenitoiteBaTiSi₃O₉hexagonal6–6.51.757–1.8053.65–3.68violetish blue, colorless, rarely pink
JeremejeviteJeremejeviteAl₆B₅O₁₅(F,OH)₃hexagonal6.5–7.51.637–1.6533.28–3.31colorless, pale blue, blue, yellow
PoudretteitePoudretteiteKNa₂B₃Si₁₂O₃₀hexagonal51.511–1.5322.51–2.53colorless to pale pink, purple-pink
SerendibiteSerendibiteCa₂(Mg,Al)₆(Si,Al,B)₆O₂₀triclinic6.5–71.701–1.7063.42–3.52grayish blue, blue-green, black
PearlNacre (calcium carbonate)CaCO₃organic2.5–31.52–1.692.6–2.85white, black, gray, yellow, orange, pink, lavender, green, blue
AmberFossil resinC₁₀H₁₆Oorganic2–2.51.541.08yellow, orange, brown; rarely blue or green
Precious coralCoralliidae skeletonCaCO₃ (calcite)organic3.51.486–1.6582.8white, pink, salmon, red
JetLigniteC with impuritiesorganic2.5–41.661.19–1.35black to dark brown
(Fig. 04)Species treeSpecies → variety

One mineral,
many names.

Ruby and sapphire are both corundum. Emerald and aquamarine are both beryl. The trade names follow color; the species follows chemistry and structure.

Fig. 01.2

Species and their varieties

10 species → 36 trade varieties

  1. DiamondC
    • Yellow (canary)yellowNitrogen (isolated N gives canary yellow)
    • Blueblue to grayish blueBoron (type IIb)
    • Pinkpink to redLattice defects from plastic deformation
    • GreengreenVacancies (GR1) from natural radiation
  2. CorundumAl₂O₃
    • Rubyorangy red to purplish redCr³⁺
    • Blue sapphireblueFe²⁺–Ti⁴⁺ intervalence charge transfer
    • Pink sapphirepinkCr³⁺
    • Yellow sapphireyellowFe³⁺ and trapped-hole (h•–Fe³⁺) centres
    • Color-change sapphirechanges between daylight and lamplightV³⁺
  3. BerylBe₃Al₂Si₆O₁₈
    • Emeraldgreen to bluish greenCr³⁺ and/or V³⁺
    • Aquamarinepale blue to greenish blueFe²⁺
    • Morganitepink to peachMn²⁺
    • Heliodorgreenish yellowFe³⁺
    • Red berylredMn³⁺
    • GoshenitecolorlessNo significant chromophore
  4. ChrysoberylBeAl₂O₄
    • Alexandritegreen in daylight, red in incandescent lightCr³⁺
    • Cat’s-eye (cymophane)yellowish with a bright chatoyant bandParallel needles or tubes (chatoyancy)
  5. QuartzSiO₂
    • Amethystviolet to purpleFe³⁺ plus natural irradiation
    • Citrineyellow to orangeFerric iron; most is heated amethyst
    • Smoky quartzbrown to gray-blackAl color centers from natural radiation
    • Rose quartzpale pinkDumortierite-related mineral fibers
    • Chrysopraseapple greenNickel compounds
  6. Elbaite (tourmaline)Na(Li₁.₅Al₁.₅)Al₆Si₆O₁₈(BO₃)₃(OH)₄
    • Rubellitepink to redManganese
    • IndicoliteblueIron
    • Paraíbaneon blue to greenCu²⁺ (with Mn)
  7. SpinelMgAl₂O₄
    • Red spinelred to pinkCr³⁺
    • Blue spinelblue to violetFe²⁺
    • Cobalt spinelsaturated blueCo²⁺
  8. SpodumeneLiAlSi₂O₆
    • Kunzitepink to violetManganese
    • HiddenitegreenCr³⁺
  9. Pearl (organic, not a mineral)Aragonite CaCO₃ platelets bound by conchiolin
    • Natural pearlwhite, cream, grey, black or goldenFormed without human intervention; nacreous or non-nacreous
    • Cultured pearlwhite, silver, golden, grey to blackGrown after a bead or tissue graft is inserted by hand
    • Composite pearlvaries with the assembled partsTwo or more parts joined, at least one of them pearl or nacre
    • Imitation pearlany, matched to the pearl being copiedManufactured; glass or plastic under a pearlescent coating
  10. Olivine(Mg,Fe)₂SiO₄
    • Peridotyellowish green to greenIron (Fe²⁺) in the olivine structure, not a trace element
    • Meteoritic peridotyellowish greenThe same iron; crystals found in pallasite meteorites
(Fig. 05)HardnessMohs 1 to 10

Ten steps,
not ten equal steps.

Mohs ranks minerals by which scratches which. Measured on a hardness tester, diamond is several times harder than corundum, the next step down. Select a bar to compare.

Fig. 03.2

Mohs scale against measured hardness

  1. 1
  2. 2
  3. 3
  4. 4
  5. 5
  6. 6
  7. 7
  8. 8
  9. 9
  10. 10

Selected

Diamond

Mohs
10
Vickers (GPa)
115
vs. step below
5.9×

Vickers microhardness in GPa (Broz, Cook & Whitney 2006) Equal steps (if Mohs were linear)

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