The Gemstone Library
A professional reference covering optical and physical properties, geographic origins, treatment detection and identification equipment, structured for gemmologists, jewellers and serious collectors.
Identification requires more than a name
A gemstone name tells you almost nothing on its own. A ruby could be a natural unheated Burmese stone worth fifty times more than a treated Thai equivalent, visually identical to the untrained eye. The difference lies in inclusions, optical properties, spectral absorption and geographic markers that only a structured reference can help you interpret.
This library organises that information around how identification actually works in practice: what you observe first under the loupe, what that observation means, which instrument to reach for next, and what the result tells you about treatment, origin and species. Each entry is a workflow, not just a data sheet.
The reference spans 144 gemstone entries across 38 mineral families, 70 producing origins in 56 countries, 17 diagnostic inclusion types and 33 treatment profiles, all cross-linked so that a property observed in one entry points directly to the tools, treatments and origins relevant to it.
The three-step process
Visual assessment
Before any instrument, the loupe reveals more than most gemmologists give it credit for. Crystal morphology, growth patterns, inclusions, colour zoning and surface features all narrow the candidate species significantly. A silk-like rutile needle network points immediately to corundum. A horse-tail inclusion to demantoid garnet. The loupe is not a preliminary step. It is often the decisive one.
Pleochroism, observable with the naked eye or a dichroscope, further reduces possibilities. A strongly dichroic blue stone showing violet and blue is almost certainly tanzanite or iolite, not sapphire. Each visual clue is a filter applied before any measurement is taken.
Optical testing
The refractometer provides the refractive index, arguably the single most diagnostic measurement in practical gemmology. Combined with birefringence and optic character (uniaxial or biaxial), it eliminates large groups of species with one reading. A stone with RI 1.76 and strong birefringence is zircon. At 1.54 with near-zero birefringence, it is likely glass or fluorite.
The spectroscope adds another dimension: characteristic absorption bands tied to specific colourants can confirm a chromium-bearing species, identify cobalt glass, or reveal the treated versus natural origin of a colour. These instruments together constitute the core optical battery of any field or laboratory assessment.
Physical & advanced testing
Specific gravity confirms what optics suggest and resolves ambiguities between species with overlapping RI ranges. Fluorescence under long-wave and short-wave UV often carries diagnostic value, particularly for distinguishing natural from synthetic stones or detecting certain treatments. Chelsea filter response, thermal conductivity and polariscope examination complete the standard advanced battery.
When field methods leave uncertainty, as they will for high-value stones, heated corundum, or origin determination, laboratory analysis using EDXRF, FTIR spectroscopy and photoluminescence provides definitive answers. Understanding which results require lab referral is as important as the testing itself.
Entry spotlight
Red Beryl
Raspberry red to purplish red
- Hardness
- 7.5–8 Mohs
- Refractive index
- 1.6–1.6
- Specific gravity
- 2.6–2.7
- Birefringence
- 0–0
- Crystal system
- Hexagonal
- Luster
- Vitreous
Gemstone library
Where a stone comes from changes everything
Geographic origin is not simply a point of curiosity. It is a primary determinant of value, quality expectation and market positioning. A Burmese ruby with no heat treatment commands multiples of the price of a chemically identical Thai stone. Kashmir sapphire is categorically distinct from Sri Lankan material in collector perception, even when optical properties overlap entirely.
This is because certain localities have historically produced material with characteristics (colour saturation, inclusion type, clarity) that are genuinely superior on average, and that reputation is encoded in market pricing. The origin data in this library documents those relationships: which mines produce which gems, at what prestige level, and what that means for identification and valuation context.
Explore all 70 origins →Citrine, Ametrine
Sapphire, Ruby, Rhodolite, Malaia Garnet, Color Change Garnet, Padparadscha Sapphire, Tourmaline, Zircon
Pyrope
Sapphire, Blue Sapphire
Ruby, Spinel, Sapphire
Boulder Opal
Nature's fingerprints
Every natural gemstone carries a record of its geological history in the form of inclusions: mineral crystals, fluid-filled cavities, growth tubes, fractures healed before the stone left the earth. These are not imperfections. They are the primary evidence that distinguishes natural stones from synthetics, identifies species, and in some cases points directly to a specific geographic origin.
A natural two-phase inclusion with a rounded negative crystal bubble is diagnostic of natural origin. Chevron growth in amethyst rules out citrine. A silk of fine rutile needles, partially dissolved by heat, is one of the most reliable indicators of high-temperature treatment in corundum. The 17 inclusion types documented here each carry specific diagnostic weight, and each entry explains what that weight is.
Browse inclusions →What disclosure actually requires
The gem trade has historically struggled with transparency around treatments. Heat treatment of sapphire is now so universal it is considered acceptable without specific disclosure in most markets, yet beryllium diffusion treatment of the same stone requires mandatory declaration. The distinction matters commercially, legally and ethically, and the difference is often only detectable under laboratory conditions.
Understanding treatments is not optional for anyone involved in buying or grading gemstones professionally. Each of the 33 treatment profiles in this library documents what the treatment does to the stone, what visible evidence it leaves, which tools can detect it in the field, and what the disclosure implications are. Knowing a stone has been treated is less than half the job. Knowing what kind matters far more.
Browse treatments →Essential tools
Inclusions
Treatments
- Assembled Stones, Doublets and Triplets Opal, Garnet-topped doublets, Quartz doublets,…
- Dyeing, Pearls Freshwater Pearls, Akoya Pearls, cultured…
- Resin Filling, Emerald Emerald
- Irradiation, Quartz Smoky Quartz, Amethyst, Citrine, Prasiolite…
- Quench Crackling and Dyeing Quartz, Rock Crystal, low-cost decorative…
- Irradiation and Annealing, Topaz Blue Topaz
Metals
Blog
- Refractive Index: The Single Most Useful Test in Gemstone Identification 10 May 2026
- Natural Unheated Rubies: What the Market Expects and What You Should Pay 6 May 2026
- Tanzanite vs Sapphire: How to Tell Them Apart and Which to Choose 28 Apr 2026
- The Best Gemstone Investments for 2026: A Clear-Eyed Assessment 21 Apr 2026
- How to Spot a Treated Gemstone Without Sending It to a Lab 10 Apr 2026
- Padparadscha Sapphire: Gemmology's Most Debated Colour 2 Apr 2026