Gemology Fast Track / Unit 21 of 24 · Man-made & treated · 60 min
Collector gems: learning the long tail
Goal: Learn ~100 rarer species efficiently using property clusters instead of memorising each one.
Strategy for 300+ gems in one day
1 · Learn by RI bandEach band holds 10–30 gems. Learn the 2–3 majors, then the collector 'neighbours'.
2 · One hook per gemA single distinctive feature (benitoite = blue SWUV; sphene = huge fire + doubling).
3 · FlashcardsUse the members' Flashcards tool, 'Collector' deck. 20 min sprints, mark misses.
4 · Test with ID HelperEnter a gem's numbers from memory; see what else overlaps.
Hooks for the collector gems you'll actually be offered
BenitoiteBlue, bright blue SWUV, fire ≈ diamond
SpheneFire > diamond, strong doubling, OTL
KyaniteBlue bands, hardness 4.5 one way / 7 the other
AndalusiteGreen with red-brown flashes face-up
ApatiteNeon blue-green but H5; 580 nm doublet
SinhaliteLooks like peridot, B−, SG 3.48
KornerupineGreen/brown trichroism, RI 1.66–1.68
TaaffeiteLooks like spinel but doubly refractive
PainiteOrange-brown, RI 1.79–1.82, Mogok
GrandidieriteBlue-green, bire 0.037, Madagascar
DanburiteColourless/pink, like topaz but SG 3.00
ScapoliteYellow/purple; variable RI 1.54–1.60, U−
DiasporeGreen ↔ pinkish brown colour change, Turkey
SphaleriteFire 0.156, very soft
EuclasePale blue, perfect cleavage, RI 1.65–1.67
HambergiteColourless, SG 2.35, bire 0.072
PhenakiteColourless, hard (7.5–8), RI 1.65–1.67 U+
FluoriteRI 1.43 — lowest common gem
CassiteriteSG ~7, bire 0.097
Musgravite / serendibite / jeremejeviteUltra-rare; lab ID
For ultra-rare species, the realistic skill is recognising 'not a common gem' from your numbers and sending it to a lab (Raman). Nobody IDs musgravite by loupe.
Gems in this unit (98)
Red berylPezzottaiteGahnospinelGahniteTopazoliteRainbow andraditeUvaroviteLiddicoatiteAchroiteLow zirconHerkimer quartzLodoliteFire agateHyaliteOrthoclaseSanidineBytowniteTriphaneAzuriteHackmaniteMoldaviteLibyan desert glassMarcasiteHemimorphiteFluoriteCalciteAragoniteVesuvianiteAndalusiteApatiteAxiniteBenitoiteBerylloniteBrazilianiteDanburiteDatoliteDiopsideEnstatiteEkaniteEpidoteEuclaseGrandidieriteHambergiteHaüyneJeremejeviteKornerupineKyanitePainitePetalitePhenakitePollucitePoudretteiteRhodiziteScapoliteScheeliteSillimaniteSinhaliteSphaleriteSpheneTaaffeite
Full gem records open in the members' Gem database.
Practical
Flashcards → Collector deck, 3 rounds of 20. Then ID Helper: try RI 1.757/1.804, U+, SG 3.68 and see benitoite rise to the top.
Unit quiz
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