Master the ancient craft of gemology — from optical properties to crystal systems. Your guide to identifying precious and semi-precious gems with confidence.
Padparadscha
Ceylon · Sri Lanka
RI 1.762–1.770 · SG 4.00 · Mohs 9
Why CeylonGemLuxury
Built for Sri Lanka\'s Gem Heartland
Sri Lanka — ancient Ceylon — produces some of Earth\'s finest sapphires, rubies, and cat\'s eyes. This platform gives you the scientific foundation to identify them accurately.
9
Key Properties
24
Gem Profiles
10
Mohs Levels
∞
Knowledge
Gemology Fundamentals
The 9 Key Properties of Gem Identification
Every gem can be precisely identified by measuring and observing these physical and optical properties.
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01 · Optical
Color
The most visible property. Caused by trace elements — chromium gives rubies their red, iron gives sapphires their blue. Observe hue, tone, and saturation.
"A fine Ceylon sapphire glows with a soft cornflower blue."
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02 · Optical
Luster
How light reflects off the surface. Types include adamantine (diamond), vitreous (glass-like), resinous, silky, and pearly. Critical first clue.
Diamond\'s adamantine luster is unmatched in nature.
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03 · Optical
Refractive Index
How much light bends entering the gem. Measured with a refractometer. Diamond = 2.42, Ruby = 1.76–1.77, Quartz = 1.54–1.55.
The single most precise identification tool available.
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04 · Physical
Hardness
Resistance to scratching, measured on the Mohs scale (1–10). Diamond is 10, corundum (ruby/sapphire) is 9, emerald is 7.5–8.
Never scratch — use the scale conceptually, not literally on fine gems.
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05 · Physical
Specific Gravity
The density of the gem relative to water. Diamond = 3.52, Ruby = 4.00, Emerald = 2.71. Measured by hydrostatic weighing.
Two gems of identical size can feel dramatically different in weight.
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06 · Structural
Crystal System
The geometric arrangement of atoms. 7 systems: cubic, tetragonal, orthorhombic, hexagonal, trigonal, monoclinic, triclinic. Determines cleavage and shape.
Some gems show different colors when viewed from different angles. Tanzanite shows blue, violet, and burgundy. Alexandrite shows green and red under different light.
Observed with a dichroscope — a gemologist\'s essential tool.
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08 · Optical
Fluorescence
Reaction under ultraviolet (UV) light. Many diamonds fluoresce blue under UV. Rubies often fluoresce red. A useful supplementary test.
Never rely on fluorescence alone — use it to confirm other findings.
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09 · Internal
Inclusions
Internal features — crystals, needles (rutile silk), feathers, fingerprints. Viewed under magnification. Nature\'s fingerprint — each gem is unique.
Ceylon sapphires often show fine rutile silk — a mark of authenticity.
The Gem Atlas
Precious & Semi-Precious Gem Profiles
Detailed profiles of the world\'s most prized gems — with special focus on Sri Lanka\'s legendary stones.
Identification Method
The Ceylon Gem Luxury Identification Protocol
Follow this systematic method — used by professional gemologists — to accurately identify any unknown gem.
Step-by-Step Process
Work through each step in order. Rule out possibilities at each stage.
1
Visual Observation
Examine color, transparency, luster, and overall appearance with the naked eye. Note any optical phenomena (asterism, chatoyancy, adularescence).
2
Check the Luster
Is it adamantine, vitreous, resinous, or silky? Adamantine luster immediately points to diamond, demantoid, or high-RI materials.
3
Measure Refractive Index (RI)
Use a refractometer. This single reading eliminates the majority of possibilities. Note if singly or doubly refractive.
4
Test Specific Gravity (SG)
Weigh the gem in air and in water. SG = weight in air ÷ (weight in air − weight in water). Confirms identity when combined with RI.
5
Examine Inclusions Under Magnification
Use a 10× loupe or microscope. Look for growth patterns, crystal inclusions, needles, or fingerprints that are species-specific.
6
Check UV Fluorescence
Test under both long-wave and short-wave UV. Note the colour and intensity. Record as strong, medium, weak, or inert.
7
Check Pleochroism
Use a dichroscope to observe if different colours appear from different angles. This separates many look-alike gems.
8
Cross-Reference & Conclude
Compare your data against reference tables. When RI + SG + inclusions all match — you have a positive identification.
Hardness Reference
The Mohs Scale of Hardness
Devised by Friedrich Mohs in 1812, this 1–10 scale measures scratch resistance. Each step represents a significant difference in hardness.
Knowledge Test
Test Your Gem Knowledge
10 questions covering gem properties, identification methods, and famous Sri Lankan gems.
Virtual Lab
Gem Identification Lab
A mystery gem is placed before you. Study its properties carefully — colour, luster, refractive index, hardness, and special features — then identify it.
Difficulty:
Gemologist\'s Toolkit
How to Identify Gems Using Professional Tools
Colour is visible to the naked eye — but luster, hardness, refractive index and specific gravity need the right tools. Here is everything you need to know.
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Luster
How light reflects off the gem surface. Observed with the naked eye or a 10× loupe. The fastest and first identification clue — takes only 3 seconds.
No instrument neededFreeFirst step always
How to observe
Hold the gem under a single directional light — a window or pen torch. Watch how the surface reflects. Rotate slowly. Observe the surface, not the inside of the gem.
Tap a luster type to learn more:
Adamantine
Diamond, zircon, demantoid garnet
Vitreous
Sapphire, ruby, emerald, topaz, amethyst
Resinous
Amber, hessonite garnet, sphalerite
Silky
Tiger\'s eye, satin spar, fibrous malachite
Pearly
Pearl, moonstone
Waxy
Jade, turquoise, opal, chalcedony
Metallic
Hematite, pyrite, native gold
Sub-metallic
Magnetite, chromite, cassiterite
Sri Lanka tip
Ceylon sapphires and rubies always show vitreous luster — like clean glass. If a "sapphire" shows waxy or resinous luster, it is likely glass or synthetic. Always check luster first.
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Hardness — Mohs Pick Set
Scratch resistance measured on the Mohs scale 1–10. Test only on an inconspicuous spot. Never scratch facets of a finished gem.
Tool: Hardness picks$25–$60 USDUse with caution
1
Get a hardness pick set — 9 metal-tipped picks of calibrated Mohs hardness 1–9. Available from Mineralab, Kruss, or Amazon ($25–60).
2
Clean the gem surface — dust or grit can give false scratch marks. Wipe with a soft cloth.
3
Start below the suspected hardness — try a lower pick first. If it cannot scratch the gem, the gem is harder than that pick.
4
Apply light pressure — drag the tip across an inconspicuous area. Use a loupe to check whether the gem was scratched or you only scratched the pick tip.
5
Confirm both ways — if pick 8 scratches the gem but pick 7 does not, the hardness is between 7 and 8.
⚠️
Never test on facets of a finished gem. Even a tiny scratch permanently damages the polish and value. For set or faceted gems, rely on RI and SG instead.
Alternative tests — no picks needed
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Unglazed ceramic tile (Mohs ~6.5) — drag the gem across the tile. If it leaves a coloured mark, the gem is softer than 6.5. Sapphire (9) leaves no mark. Fluorite (4) leaves a mark.
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Glass plate (Mohs ~5.5) — a gem harder than 5.5 scratches the glass. Sapphire, ruby, topaz, emerald all scratch glass easily. A useful quick test at any gem market.
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Steel nail file (Mohs ~6.5) — if a file scratches the gem, hardness is below 6.5. Cannot distinguish between 7 and 10 — useful only to rule out very soft material.
Measures how much light bends as it enters the gem. The single most important identification test — each gem has a unique RI value.
Tool: Gem refractometer$80–$300 USDMost reliable test
Entry level
$80–120
Manual, range 1.40–1.81 RI
Mid range
$150–200
Built-in LED, no filter needed
Professional
$250–600
Duplex II, Rayner — lab grade
Digital PRIM II
$400+
No RI liquid, reads up to 3.000
1
Apply one drop of RI contact liquid (refractive index oil, n=1.81) to the glass hemisphere of the refractometer.
2
Place the gem face-down on the glass, flat polished facet touching the oil. The oil creates optical contact between gem and glass.
3
Look through the eyepiece — you see a scale from 1.40 to 1.81. A dark shadow edge appears on the scale. Read the number at the shadow boundary.
4
Rotate the polarising filter — if the shadow edge moves up and down, the gem is doubly refractive. If it stays fixed, it is singly refractive (glass, garnet, spinel).
5
Compare your reading to the reference table below. Blue Sapphire = 1.762–1.770. Ruby = 1.762–1.770. Emerald = 1.577–1.583.
⚠️
Standard refractometers cannot read above 1.81 RI — so diamond (2.42) and zircon (1.81–1.98) fall off the scale. Use a Presidium PRIM II digital refractometer or a diamond thermal tester for these.
Key RI values — Sri Lankan gems
Blue Sapphire
1.762–1.770
Ruby
1.762–1.770
Cat\'s Eye
1.745–1.754
Alexandrite
1.746–1.755
Moonstone
1.518–1.526
Spinel
1.718
Zircon
1.810–1.984
Emerald
1.577–1.583
Recommended brand
Gain Express GR-701B (~$99, built-in LED + RI oil included) is excellent value for Sri Lanka gem buyers. Duplex II by GIA ($300+) for professional lab work. Presidium PRIM II ($400) if you need to test diamonds without liquid.
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Specific Gravity — Hydrostatic Scale
Measures gem density by weighing in air then in water. Combined with RI, this confirms identity with near certainty.
Tool: Digital scale + hydrostatic kit$50–$250 USDConfirms identity
SG Calculator — try it
SG = Weight in air ÷ (Weight in air − Weight in water)
SG = 4.03
→ Likely: Ruby / Sapphire (4.00)
1
Weigh the gem in air on a precise digital scale (0.001g precision). Record as Wair.
2
Suspend the gem in water using a fine wire basket hanging from the scale. Ensure fully submerged, not touching container sides.
3
Weigh the gem in water. Record as Wwater. The difference is the weight of water displaced by the gem.
4
Apply the formula — SG = Wair ÷ (Wair − Wwater). Use the calculator above.
The gem must be clean and dry before weighing in air, and free of trapped air bubbles in water. For gems under 0.5ct, even tiny weighing errors affect the SG result significantly — for small stones, rely on RI alone.
SG reference — Sri Lankan gems
Sapphire / Ruby
4.00
Cat\'s Eye / Alex.
3.71–3.73
Spinel
3.60
Zircon
4.65
Emerald / Aquamarine
2.71
Moonstone
2.57
Amethyst
2.65
Opal
2.10
Equipment needed
A digital precision scale with 0.001g resolution ($50–150) + hydrostatic wire basket kit ($20–50). Or a dedicated hydrostatic balance ($80–200). The Kassoy or Pretty Rock travel SG kit (~$40) is ideal for Sri Lanka field use.
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Recommended Starter Kit
Everything a beginning gemologist needs for Sri Lanka\'s gem markets. Build your kit gradually — start with the essentials.
Budget kit ~$200Full kit ~$500–700
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10× Triplet Loupe
$15–$50 · Buy this first
Your most-used tool. Examine inclusions, luster, surface condition, and cut quality. Get a darkfield loupe — shows inclusions far more clearly.
Essential
🔭
Gem Refractometer
$80–$150 · Most important
Gain Express GR-701B has built-in LED and comes with RI oil. Gives the single most reliable reading. Buy this second after a loupe.
Essential
🌊
UV Lamp (dual-wave)
$25–$60 · Great value
Reveals fluorescence. Rubies glow red, many diamonds glow blue. Essential for separating ruby from garnet. Get long-wave + short-wave.
Essential
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Precision Digital Scale
$30–$80 · For SG testing
0.001g precision. Used with a hydrostatic kit to measure specific gravity. Also weighs gems in carats (1ct = 0.2g). American Weigh Scales brand is reliable.
Essential
🔬
Polariscope
$30–$130 · Next level
Determines if a gem is singly or doubly refractive. Separates glass from real gems instantly. Handheld models ($30) work perfectly for field use.
Advanced
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Dichroscope (calcite)
$30–$60 · Pleochroism
Reveals pleochroism — different colours from different angles. Key for identifying tanzanite, alexandrite, iolite. Calcite type is better than filter type.
Advanced
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Chelsea Filter
$15–$30 · For emerald & jade
Makes chromium-coloured gems (real emerald) glow red. Very useful for emerald identification at markets. Pocket sized — carry always.
Advanced
🔬
Gem Microscope
$200–$800 · Lab level
10×–45× magnification with darkfield illumination. See inclusions in stunning detail — rutile silk in sapphires, jardin in emeralds. Buy when you are ready to go professional.
Lab level
Ratnapura field priority
At a Ratnapura or Galle gem market, carry: (1) a 10× darkfield loupe in your pocket, (2) a UV torch for quick fluorescence check, (3) a refractometer in your bag. These three correctly identify 90% of Sri Lankan gems in under 5 minutes.
Budget starter route
Darkfield loupe ($40) + Gain Express refractometer with LED ($99) + dual UV lamp ($35) + digital scale ($30) = approx. $200 total. Enough to identify all major Sri Lankan gems with confidence.
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5-Step Gem Identification Protocol
A professional workflow for identifying any unknown gem — especially when buying in Sri Lanka. Follow these 5 steps in order. Each step narrows down the possibilities until only one gem matches.
Field-tested workflowWorks for all gem typesUsed by professionals
1
Visual
10× Triplet Loupe & Pen Torch
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Primary Tool
10× Darkfield Triplet Loupe + Pen Torch
$15–$60 USD
What it tells you: Whether inclusions inside the gem are natural or man-made. Natural gems contain irregular, fingerprint-like inclusions — liquid feathers, crystal needles, growth zoning. Glass and synthetics show round gas bubbles, curved growth lines, and swirl patterns.
✓
Examine under oblique pen torch light. Look for irregular fingerprint inclusions — these are natural.
✓
Round gas bubbles = glass or synthetic. Curved striae (wavy lines) = Verneuil synthetic corundum.
✓
In Ceylon sapphires: look for fine rutile silk needles — a strong indicator of natural origin.
ResultNatural vs synthetic/glass — and initial luster clue for mineral family.
2
Thermal
Presidium Gem Tester II (PGT II)
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🌡️
Primary Tool
Presidium Gem Tester II (PGT II)
$50–$120 USD
What it tells you: The basic mineral family instantly — proves whether the gem is Corundum, Topaz, Beryl, Quartz, etc. Each mineral conducts heat at a different rate. The tester gives a needle reading on a scale that maps to mineral families. This single step eliminates most impostors.
✓
Touch the probe tip to a clean, polished facet. Hold steady for 2–3 seconds until the needle stabilises.
✓
Read the needle position against the gem scale printed on the tester. Corundum (sapphire/ruby) gives a distinctive reading.
✓
Glass reads at the far low end. Diamond reads beyond the scale (use a dedicated diamond tester instead).
⚠
Limitation: cannot distinguish ruby from sapphire (both corundum) or separate gems with similar thermal conductivity. Confirms family, not exact species.
ResultConfirms mineral family — e.g. "this is Corundum" (not glass, not quartz, not topaz).
3
Density
Specific Gravity Kit — SG 50
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⚖️
Primary Tool
Specific Gravity Kit (SG 50 or equivalent)
$40–$150 USD
What it tells you: The exact mineral group by measuring density. Each mineral has a precise, characteristic SG value. Corundum is always ~4.00 — if your blue stone measures 3.60 it is spinel, if 2.65 it is glass or quartz. This step confirms what Step 2 suggested.
✓
Weigh the gem in air (Wair) on a 0.001g precision scale. Record the reading.
✓
Suspend the gem fully in water using the wire basket. Weigh again (Wwater). Calculate: SG = Wair ÷ (Wair − Wwater).
For gems under 0.5ct, even a 0.01g weighing error causes a large SG error — use RI instead for small stones.
ResultConfirms the exact mineral group — e.g. SG 4.00 proves Corundum, separating it from all look-alikes.
4
Optical
Dichroscope
▼
👁
Primary Tool
Calcite Dichroscope
$30–$60 USD
What it tells you: Double refraction — proving that the gem splits light into two rays. All corundum (sapphire, ruby) is doubly refractive. Glass and cubic spinel are singly refractive. This step definitively separates sapphire from glass or spinel look-alikes and reveals pleochroism (different colours from different directions).
✓
Hold the dichroscope up to a strong light source. Place the gem against the opening. Look through the eyepiece — you see two coloured windows side by side.
✓
If the two windows show DIFFERENT colours — the gem is doubly refractive (most natural coloured gems including sapphire and ruby).
✓
If both windows show the SAME colour — singly refractive (glass, cubic spinel, garnet). Sapphire showing the same colour in both windows from all directions = likely glass or spinel.
✓
Rotate the gem in all directions — the colours in the two windows change as you rotate. Record the distinct colours seen. Tanzanite shows 3 colours (blue, violet, burgundy) — a signature result.
ResultProves double refraction — separates sapphire/ruby from glass, cubic spinel, and other singly refractive look-alikes.
5
Light Spectrum
Chelsea Filter & Spectroscope
▼
🌈
Primary Tools
Chelsea Filter + Hand Spectroscope
$15–$80 USD combined
What it tells you: The chemical signature of colour — exposing artificial colour components, synthetic dyes, or chemical treatment profiles. The Chelsea filter uses selective wavelength transmission to reveal chromium. The spectroscope reveals the characteristic dark absorption bands caused by trace elements — a chemical fingerprint unique to each gem species.
✓
Chelsea Filter: Hold against a strong white light. View the gem through the filter. Chromium gems (real emerald, some red gems) glow red-orange. Non-chromium green gems (e.g. glass tinted green, tourmaline) appear green.
✓
Spectroscope: Direct strong white light through the gem into the spectroscope. Look for dark bands in the colour spectrum. Ruby/red spinel both show a chromium doublet at 693nm and 694nm — but ruby also shows an extra band at 476nm.
✓
Synthetic dye detection: Artificially coloured stones (dyed quartzite, glass) show unusual, broad absorption without the sharp characteristic bands of natural chromium or iron colouring.
✓
Key spectroscope readings: Blue sapphire — iron bands at 450nm. Ruby — chromium doublet 693–694nm + band at 476nm. Emerald — chromium doublet 683–680nm. Hessonite garnet — no bands (inert).
ResultReveals chemical colouring agent — separates natural from treated or synthetic, and identifies specific species within a mineral family.
Protocol Summary
Step
Type
Tool
What It Tells You
Price
1
Visual
10× Loupe + Pen Torch
Natural vs synthetic — inclusions, luster, surface
$15–60
2
Thermal
Presidium PGT II
Mineral family — corundum vs topaz vs quartz
$50–120
3
Density
SG Kit (scale + basket)
Exact mineral group — SG 4.00 = corundum confirmed
$40–150
4
Optical
Dichroscope
Double refraction — separates sapphire from glass/spinel
$30–60
5
Light Spectrum
Chelsea Filter + Spectroscope
Chemical signature — natural colour vs synthetic/treated
$15–80
Field tip for Ratnapura market
Steps 1, 4, and 5 (loupe, dichroscope, Chelsea filter) are pocket-sized and can be done standing at a gem dealer\'s table in under 3 minutes. Steps 2 and 3 (PGT II and SG kit) are done back at your room or lab to confirm. Together, all 5 steps give you a near-certain identification without a laboratory certificate.
Live Gem Market
Gewda Stones & Gem Sales Sri Lanka — Last 24 Hours
One-click search links to find the latest Gewda stone listings posted in Sri Lanka\'s active gem selling communities on Facebook, Google, and direct dealer groups.
How this works: Each button below opens a targeted search — filtered to the last 24 hours — directly inside Facebook or Google. You land on real, current posts from Sri Lankan gem sellers. No login required for Google searches. Facebook searches work best when you are logged in.
Google indexes public Facebook posts. These links search Google filtered to facebook.com + last 24 hours — the fastest way to find recent gem listings.
Always verify gems using the identification methods on this website before purchasing. Request a GIA or GRS certificate for stones above $500. Never send payment before receiving the stone — use escrow or trusted dealers in Ratnapura.
Pro Tips for Finding Gem Posts
Sort by "Latest" — After opening any Facebook search, click "Latest" or "Recent" at the top to see the newest posts first, not the algorithm\'s picks.
Join active groups — Groups like "Sri Lanka Gem Traders", "Ratnapura Gem Market" post daily. Once you join, posts appear in your Facebook feed automatically.
Google finds hidden posts — Google indexes public Facebook posts that Facebook\'s own search often hides. Use the Google 24h links above for the freshest results.
Sinhala keywords work better — Try searching "ගෑදා ගල්" (Gewda stones in Sinhala) on Facebook for posts that English search misses.
Facebook Marketplace — Often has cleaner listings with photos and prices upfront. Sellers in Ratnapura and Colombo list here daily.
Bookmark this page — Come back daily. All search links always query the latest 24 hours — the results update automatically each time you click.
