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Identifies gemstones using optical properties, physical tests, and inclusion analysis. Useful for unknown specimens, verifying seller claims, and distinguishing natural stones from simulants.
How this skill is triggered — by the user, by Claude, or both
Slash command
/agent-almanac:identify-gemstoneThis skill is limited to the following tools:
The summary Claude sees in its skill listing — used to decide when to auto-load this skill
Identify gemstones using systematic physical and optical property testing, inclusion analysis, and elimination against known species profiles.
Identify gemstones using systematic physical and optical property testing, inclusion analysis, and elimination against known species profiles.
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 |
+--------------------+------------------------------------------+
Expected: A complete visual profile including colour, transparency, luster, and any phenomena. This alone narrows candidates to a manageable shortlist.
On failure: 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.
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 |
+--------------------+------------------------------------------+
Expected: 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.
On failure: 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.
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 |
+--------------------+------------------------------------------+
Expected: RI value (to 0.001), birefringence, optic character, pleochroism description, and UV response. Combined with Step 2, this identifies most gemstone species definitively.
On failure: 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.
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 |
+------------------+------------------------------------------+
Expected: 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).
On failure: 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.
Cross-reference all collected data to reach a final identification.
Expected: 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.
On failure: 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.
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