Learn Gemmology¶

FGA curriculum-aligned content covering crystallography, physical and optical properties, chemical properties, inclusions, treatments, synthetics, gem testing instruments, phenomenal gems, origin determination, grading, and professional practice.

Interactive Content

For the best learning experience with interactive crystal visualizations and structured data tables, visit gemmology.dev/learn.

Fundamentals¶

Crystal Systems ¶

The seven crystal systems and their characteristic symmetry elements. Learn about axes, angles, and how crystal structure affects gemstone properties.

Advanced Crystallography ¶

Twinning, Miller indices deep dive, crystal habits, the 32 point groups, and crystal growth mechanisms. Essential for FGA Diploma.

Physical Properties ¶

Hardness, specific gravity, cleavage, fracture, lustre, and tenacity. Includes SG measurement techniques, directional hardness, and thermal conductivity.

Chemical Properties ¶

Gem chemistry, chromophores and colour causes, allochromatic vs idiochromatic minerals, charge transfer mechanisms, and colour centres.

Optical Properties ¶

Refractive index, birefringence, pleochroism, dispersion, and absorption spectra. The most important diagnostic features for gem identification.

Advanced Optical Properties ¶

Interference figures, optic sign determination, complete absorption spectra reference, luminescence, and anomalous double refraction (ADR).

Identification¶

Gem Testing Instruments ¶

Comprehensive guide to refractometer, polariscope, dichroscope, spectroscope, Chelsea filter, UV lamp, and microscope. Essential practical skills for FGA Foundation.

Inclusions ¶

Diagnostic inclusions and fingerprinting techniques. Covers corundum, emerald, diamond, garnet, spinel, and more. Learn to identify gemstones and determine origin through their internal features.

Treatments ¶

Heat treatment, filling, diffusion, coating, irradiation, HPHT diamond treatment, and detection methods. Includes treatment stability chart and laboratory report terminology.

Synthetics ¶

Synthetic gem production methods including flame fusion, flux growth, hydrothermal, CVD, and HPHT diamond. Detection techniques, historical timeline, and market evolution.

Composite Stones ¶

Doublets, triplets, and assembled stones including opal doublets, garnet-topped doublets, and soudé emeralds. Detection methods and disclosure requirements.

Advanced Topics¶

Phenomenal Gems ¶

Optical phenomena including asterism (star effect), chatoyancy (cat's eye), adularescence, labradorescence, play of colour, colour change, and aventurescence.

Origin Determination ¶

Geographic origin determination for gemstones. Kashmir sapphire, Burmese ruby, Colombian emerald, and more. Inclusion suites, trace elements, and origin premiums.

Grading and Valuation ¶

Colour grading (hue, tone, saturation), clarity assessment, cut quality, carat weight, and value factors. Professional grading techniques for coloured gemstones.

Gem Care and Durability ¶

Gemstone stability, cleaning methods (ultrasonic, steam, safe practices), setting recommendations, and storage guidelines. Jewellery suitability by gem species.

Professional Practice ¶

Report writing, disclosure requirements, legal aspects, professional ethics, and laboratory certification. CIBJO terminology and trade organisation standards.

Supplementary Content¶

Diamond ¶

Diamond type classification (Ia, IaA, IaB, Ib, IIa, IIb), the 4Cs grading system, fancy colours, natural vs lab-grown identification, and verification instruments.

Organic Gems ¶

Pearl (natural, cultured, saltwater, freshwater), coral, amber, jet, shell materials, and ivory alternatives. Grading factors and special care requirements.

FGA Curriculum Alignment¶

This content is aligned with the Gem-A (Gemmological Association of Great Britain) FGA diploma curriculum:

Foundation Coverage: - Crystal systems and physical properties - Optical properties and gem testing instruments - Introduction to inclusions, treatments, and synthetics - Basic gem identification techniques

Diploma Coverage: - Advanced crystallography and optical properties - Origin determination and inclusion fingerprinting - Treatment detection and synthetic identification - Grading, valuation, and professional practice - Phenomenal gems and special optical effects

While comprehensive, this resource is not a substitute for formal gemmological education and hands-on training with reference stones.

Data Format¶

The learn content is stored as structured YAML data files that can be rendered by multiple platforms:

gemmology.dev - Interactive web experience with crystal visualizations
MkDocs - Static documentation site (this site)
API - Programmatic access to gemmological data

Source files are located in docs/learn/*.yaml.