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About gemmology.dev

gemmology.dev is an open, FGA-aligned reference and study toolkit for coloured gemstones. Everything here – the 159-mineral family reference, 216 crystal expressions, the Crystal Description Language (CDL), the calculators, and the quiz – is free and open-source.

Maintainer

Fabian Moor (Bissbert on GitHub), Gemmologist — Fellow of the Gemmological Association (FGA), trained at the Gem and Jewellery Institute of Thailand (GIT) in Bangkok. Contributions, corrections, and source citations from the gemmological community are welcomed via GitHub issues.

The maintainer also runs a gemstone atelier at jewlarray.ch, where the sourcing and disclosure practices described here are applied commercially.

Editorial standards

  • Curriculum alignment. Reference content follows the published Fellowship of the Gemmological Association (FGA) Diploma syllabus structure for crystal systems, optical and physical properties, equipment, and identification.
  • Numerical data. Refractive index, specific gravity, birefringence, and dispersion ranges are sourced from peer-reviewed gemmological references and verified across multiple sources before inclusion.
  • Crystal morphology. Crystal structures are described using CDL (a domain-specific language documented at /docs/cdl), rendered from formal Miller indices and point-group symmetry rather than artistic impressions.
  • Synthetics & simulants. Lab-grown materials are labelled by growth method (CVD, HPHT, flux, hydrothermal, Verneuil, Czochralski) and linked to their natural counterparts where one exists.
  • Reviewed dates. Each learn article shows when it was last reviewed. Out-of-date pages are flagged for refresh.

Sources

All factual claims in the learn articles are sourced from peer-reviewed gemmological literature, FGA curriculum materials, and vetted online references. The complete bibliography is available at Sources & bibliography.

What is not here

  • Commercial appraisals or price guidance
  • Real-time market or auction data
  • Authentication or certification: gemmology.dev is a study tool, not a lab

Reporting an error

Spotted incorrect data, a missing reference, or a broken figure? Open an issue at github.com/gemmology-dev/gemmology.dev/issues. Corrections are usually shipped within a week.

Licence

Code is MIT-licensed. Educational content (the learn articles and curriculum data in gemmology-knowledge) is published under CC BY-SA 4.0.