Identify Gemstone

Identify gemstones using systematic physical and optical property testing, inclusion analysis, and elimination against known species profiles.

适用场景

• You have an unknown gemstone or suspect gemstone and want to identify the species
• You need to verify a seller's claim about a gemstone's identity
• You want to distinguish a natural gemstone from a common simulant or synthetic
• You are building gemological literacy through structured observation and testing
• You need to identify rough material before cutting to ensure safe handling

输入

• 必需: A gemstone specimen (loose stone preferred; mounted stones limit testing)
• 可选: Refractometer with contact liquid (RI fluid, 1.81 standard)
• 可选: Dichroscope (for pleochroism testing)
• 可选: Chelsea colour filter
• 可选: Specific gravity balance or heavy liquids
• 可选: 10x loupe or gemological microscope
• 可选: UV lamp (long-wave 365nm and short-wave 254nm)
• 可选: Polariscope (for optic character determination)

步骤

第 1 步：Visual Inspection

Examine the specimen with the unaided eye and then under 10x magnification.

Visual Inspection Checklist:
+--------------------+------------------------------------------+
| Observation        | Record                                   |
+--------------------+------------------------------------------+
| Colour             | Hue (red, blue, green...), saturation    |
|                    | (vivid, moderate, weak), tone            |
|                    | (light, medium, dark)                    |
+--------------------+------------------------------------------+
| Transparency       | Transparent, translucent, opaque         |
+--------------------+------------------------------------------+
| Luster             | Adamantine, vitreous, waxy, pearly,      |
|                    | silky, resinous                          |
+--------------------+------------------------------------------+
| Cut style          | Faceted, cabochon, carved, rough         |
+--------------------+------------------------------------------+
| Estimated size     | Approximate dimensions (mm) and weight   |
+--------------------+------------------------------------------+
| Surface condition  | Scratches, chips, abrasion, wear pattern |
+--------------------+------------------------------------------+
| Phenomena          | Star (asterism), cat's eye               |
|                    | (chatoyancy), play of colour, colour     |
|                    | change, adularescence                    |
+--------------------+------------------------------------------+

1. Note the body colour under daylight-equivalent lighting (5500-6500K)
2. Check for colour zoning by viewing through the stone from different angles
3. Assess transparency and luster — these narrow the candidate list immediately
4. Look for optical phenomena (star, cat's eye, play of colour)
5. Record any visible inclusions without magnification

预期结果： A complete visual profile including colour, transparency, luster, and any phenomena. This alone narrows candidates to a manageable shortlist.

失败处理： If lighting is poor (yellowish indoor light), note the limitation. Daylight or daylight-equivalent bulbs are strongly preferred. Incandescent light shifts colour perception and can cause misidentification of colour-change stones.

第 2 步：Physical Property Testing

Test measurable physical properties to narrow the identification.

Key Physical Properties:
+--------------------+------------------------------------------+
| Property           | Method                                   |
+--------------------+------------------------------------------+
| Hardness (Mohs)    | Scratch test against reference minerals  |
|                    | or hardness pencils. CAUTION: Do NOT     |
|                    | scratch faceted gemstones — use other    |
|                    | tests instead for cut stones             |
+--------------------+------------------------------------------+
| Specific gravity   | Hydrostatic weighing:                    |
| (SG)               | SG = weight in air / (weight in air -    |
|                    | weight in water)                         |
|                    |                                          |
|                    | Common SG values:                        |
|                    | Quartz: 2.65                             |
|                    | Beryl: 2.68-2.74                         |
|                    | Tourmaline: 3.02-3.26                    |
|                    | Topaz: 3.53                              |
|                    | Corundum: 3.99-4.01                      |
|                    | Zircon: 4.60-4.73                        |
|                    | CZ: 5.65-5.95                            |
+--------------------+------------------------------------------+
| Heft               | Does the stone feel heavier or lighter   |
|                    | than expected for its size?              |
|                    | CZ and zircon feel noticeably heavy      |
|                    | Quartz and glass feel average            |
+--------------------+------------------------------------------+

1. For rough material: test hardness using Mohs scale reference points
2. For cut stones: measure specific gravity using hydrostatic method
3. Assess heft — experienced handlers can distinguish CZ from diamond by weight alone
4. Note any cleavage planes visible on the surface

预期结果： Hardness range (for rough) or SG value (for cut stones) that differentiates between candidate species. SG is often the most powerful single diagnostic for cut stones.

失败处理： If hydrostatic balance is unavailable, use the heft test as a rough guide. Stones that feel "too heavy for their size" likely have high SG (>3.5). If hardness testing would damage a cut stone, skip to optical tests.

第 3 步：Optical Tests

Apply gemological optical instruments for definitive properties.

Optical Property Tests:
+--------------------+------------------------------------------+
| Test               | What It Reveals                          |
+--------------------+------------------------------------------+
| Refractive Index   | Measured on refractometer with RI fluid  |
| (RI)               | Diagnostic for most species:             |
|                    | Quartz: 1.544-1.553                      |
|                    | Beryl: 1.577-1.583                       |
|                    | Tourmaline: 1.624-1.644                  |
|                    | Topaz: 1.609-1.617                       |
|                    | Corundum: 1.762-1.770                    |
|                    | Spinel: 1.718                            |
|                    | Diamond: 2.417 (OTL on refractometer)    |
|                    | CZ: 2.15 (OTL on refractometer)          |
+--------------------+------------------------------------------+
| Birefringence      | Difference between high and low RI       |
| (BR)               | Quartz: 0.009                            |
|                    | Corundum: 0.008                          |
|                    | Tourmaline: 0.018-0.020                  |
|                    | Singly refractive: 0 (spinel, garnet,    |
|                    | diamond)                                 |
+--------------------+------------------------------------------+
| Pleochroism        | Colour variation with crystal direction  |
| (dichroscope)      | Strong: tourmaline, tanzanite, iolite    |
|                    | Moderate: corundum, topaz                |
|                    | None: singly refractive stones           |
+--------------------+------------------------------------------+
| Optic character    | Singly refractive (SR), doubly           |
| (polariscope)      | refractive (DR), aggregate (AGG)         |
+--------------------+------------------------------------------+
| UV fluorescence    | Long-wave and short-wave UV response     |
|                    | Diamond: often blue (LWUV)               |
|                    | Ruby: strong red (LWUV)                  |
|                    | Emerald: usually inert                   |
+--------------------+------------------------------------------+
| Chelsea filter     | Transmits deep red and yellow-green      |
|                    | Emerald (Cr): appears red/pink           |
|                    | Aquamarine: appears green                |
|                    | Blue synthetic spinel: appears red       |
+--------------------+------------------------------------------+

1. Measure RI on refractometer — take both high and low readings for birefringence
2. Test pleochroism with dichroscope — rotate slowly and note colour changes
3. Check optic character on polariscope (SR vs DR vs AGG)
4. Test UV fluorescence under both long-wave and short-wave
5. Use Chelsea filter if chromium-coloured stones are suspected

预期结果： RI value (to 0.001), birefringence, optic character, pleochroism description, and UV response. Combined with Step 2, this identifies most gemstone species definitively.

失败处理： If RI is over-the-limit (OTL, >1.81), the stone is likely diamond, CZ, zircon (high-type), or a high-RI synthetic. Use SG and thermal conductivity to differentiate. If no refractometer is available, rely on SG + visual properties + inclusions.

第 4 步：Inclusion Analysis

Examine internal features under magnification for species confirmation and natural vs. synthetic determination.

Diagnostic Inclusions by Species:
+------------------+------------------------------------------+
| Species          | Characteristic Inclusions                |
+------------------+------------------------------------------+
| Diamond          | Crystals (garnet, diopside), feathers,   |
|                  | cloud, graining, pinpoints               |
+------------------+------------------------------------------+
| Ruby/Sapphire    | Silk (rutile needles), fingerprints,     |
|                  | colour zoning (straight angular),        |
|                  | crystal inclusions                       |
+------------------+------------------------------------------+
| Emerald          | Three-phase inclusions (solid + liquid + |
|                  | gas), jardin (garden-like fractures),    |
|                  | pyrite crystals                          |
+------------------+------------------------------------------+
| Tourmaline       | Growth tubes, liquid-filled fractures    |
+------------------+------------------------------------------+
| Quartz/Amethyst  | Tiger stripes, phantoms, two-phase       |
|                  | inclusions, negative crystals            |
+------------------+------------------------------------------+

Synthetic Indicators:
+------------------+------------------------------------------+
| Synthetic Type   | Telltale Inclusions                      |
+------------------+------------------------------------------+
| Flame fusion     | Curved growth lines (striae),            |
| (Verneuil)       | gas bubbles (spherical)                  |
+------------------+------------------------------------------+
| Flux grown       | Flux fingerprints (wispy veils),         |
|                  | platinum platelets                       |
+------------------+------------------------------------------+
| Hydrothermal     | Chevron or zigzag growth patterns,       |
|                  | seed plate remnant                       |
+------------------+------------------------------------------+
| Glass simulants  | Round gas bubbles, swirl marks,          |
|                  | conchoidal fracture chips                |
+------------------+------------------------------------------+

1. Examine the stone under darkfield illumination (gemological microscope) or oblique lighting through a 10x loupe
2. Look for species-diagnostic inclusions first
3. Check for synthetic indicators — curved striae and gas bubbles are definitive for flame-fusion synthetics
4. Note the inclusion type, location, and frequency
5. Photograph inclusions if possible for records

预期结果： Species-confirming inclusion pattern and natural/synthetic determination. Some species are identified more by their inclusions than by optical properties (e.g., emerald's jardin).

失败处理： If the stone is eye-clean and no inclusions are visible at 10x, it may be a very clean natural stone or a synthetic. Lack of inclusions raises the synthetic probability — refer to optical and physical tests for confirmation. Laboratory analysis (FTIR, Raman) may be needed.

第 5 步：Identification by Elimination

Cross-reference all collected data to reach a final identification.

1. Compile the property profile:
   • Colour + transparency + luster
   • Hardness or SG
   • RI + birefringence + optic character
   • Pleochroism + UV fluorescence
   • Inclusion pattern
2. Compare against reference tables for candidate species
3. Eliminate species that conflict with any measured property
4. If two or more candidates remain, identify the distinguishing test:
   • Example: blue topaz vs. aquamarine — SG is definitive (3.53 vs. 2.70)
5. State the identification with confidence level:
   • Definitive: Multiple properties confirm a single species
   • Probable: Properties consistent with one species, but one test missing
   • Uncertain: Conflicting data or insufficient testing — laboratory referral recommended

预期结果： A final species identification (e.g., "Natural sapphire, blue, heat-treated") with supporting evidence from each test category. Or a clear recommendation for laboratory analysis if field tests are insufficient.

失败处理： If the stone cannot be identified with available equipment, document all measured properties and refer to a gemological laboratory. Provide the measured data to the lab — it accelerates their analysis.

验证清单

• Visual inspection completed under daylight-equivalent lighting
• At least two physical properties measured (hardness/SG + one other)
• RI measured and birefringence calculated (if refractometer available)
• Pleochroism tested (if dichroscope available)
• Inclusions examined under at least 10x magnification
• Identification reached by systematic elimination, not assumption
• Common simulants explicitly considered and ruled out
• Natural vs. synthetic determination made (or flagged as uncertain)

常见问题

• Trusting colour alone: Colour is the least reliable identification property. Blue stones include sapphire, topaz, aquamarine, tanzanite, iolite, spinel, glass, and CZ. Always confirm with measurable properties
• Skipping SG on mounted stones: Mounted stones limit testing, but you can still check RI, pleochroism, inclusions, and UV. Document the limitation rather than guessing
• Confusing high-RI synthetics with naturals: Flame-fusion rubies and sapphires have identical RI and SG to natural stones. Only inclusions (curved striae vs. straight growth) differentiate them
• Assuming expensive = natural: Commercial jewellery frequently contains treated, synthetic, or simulant stones. Test every stone regardless of provenance claims
• Damaging the specimen: Never hardness-test a faceted gemstone — it will leave visible scratches. Use non-destructive tests (RI, SG, inclusions) for cut stones

相关技能

• cut-gemstone — Identification determines safe cutting parameters and orientation requirements for the species
• appraise-gemstone — Positive identification is the prerequisite for any meaningful valuation
• mineral-identification — Field mineral identification methodology using physical properties (prospecting domain) shares the systematic elimination approach