The Gem Identification Challenge
oval brilliant
from the JDMIS Gem Reference

Name that Gem

A stone sits under your light. All you know is its colour and transparency. Work the bench — refractometer, polariscope, spectroscope — watch the suspects fall away, and name the gem against the clock.

8mystery stones
8instruments
229suspects from the reference
1correct answer
Compete on the leaderboards — the fastest gemmologist on each stone wins a S$300 voucher for a 2026 GT200 course.

Built on the JDMIS Gem Reference — the same data our students use. A taste of GT200 · Trade Practices 2: Gem Identification Methods.

The study collection

Eight stones from the JDMIS trays — loose gems, a cabochon, one already set in jewellery. Your lab time is the sum of every test you run. Choose your first instrument wisely.

Stone No. 1
specimen · drag to rotate
turn the stone in at least three directions — even the professionals do
lab time
0 min
tests run
0
ID Recording SheetGT200

Suspects

the instrument bench

Fastest correct identifications

Per stone — lab minutes, tie-broken by fewer tests. The top time on each stone can claim a S$300 voucher off the GT200 Classroom Immersive course.

#gemmologistlab time