Saturday, December 24, 2011

Crystallomancy

So... what do you have to know in order to earn a diploma in gemology? I did some research. The results were pretty uniform. Here is a sample from the British Gemological Association's traditional list, comprising 31 syllabus sections.

1. Gem Materials

Nature and attributes of gems and ornamental materials; factors which influence the value of a stone: beauty, durability, rarity; acceptability. Earth’s physical activity; melting, recrystallization, sedimentation, mineralization.

2. The Nature of Gem Materials

The origin and occurrence of gem minerals (elementary). Major types of gem deposit (general description): pegmatite; diamond pipe; placer; hydrothermal vein. Extraction: mining and recovery methods (outline only). Minerals, atoms, elements and chemical bonding (elementary).

...

6. The Nature of Light

The importance of light in gemmology. The nature of light. Wavelength and frequency. The electromagnetic spectrum. The visible spectrum of colour. Polarization and vibration direction.

7. Refraction

Refraction; refractive index (RI), definition and description. Singly refractive materials. Doubly refractive materials: directional properties; double refraction, polarization, optic axes. Measurement of RI; the refractometer; the principle of total internal reflection; an outline of its main component parts. The determination of birefringence using the refractometer.

8. Reflection and its Effects

External reflection: lustre. Examples of lustre. Internal reflection effects caused by inclusions; chatoyancy and asterism. Internal reflection effects caused by structural features. Iridescence: interference and diffraction. Brilliance.

...

15. Artificial Gem Materials

Artificial and synthetic gems: definitions. A brief outline of methods of production and identification of materials produced by the Verneuil flame fusion, flux melt and hydrothermal methods. Non-crystalline artificial materials: paste; plastics.

16. Imitation and Composite Gem Materials

Imitation (simulation) of gem and ornamental materials; the use of natural and artificial materials as imitations; the distinction of gem diamond from its simulants, particularly cubic zirconia (CZ). Composite (assembled) natural and artificial stones; reconstructed materials.

...

21. Structure and Properties of Gem Materials

Atomic-scale structure, electrons and chemical bonding. The crystalline state and crystalline materials. Crystal structures in terms of chemical bonding. Structural isomorphism: ‘isomorphous substitution’. Crystalline polymorphism. The relationship of crystal structure and symmetry to crystal faces, forms, habits, cleavage, internal growth phenomena and crystal surface markings; relevance to identification.

...

31. Description of Gem Materials of Organic Origin

Origin, occurrence, recovery, methods of identification and common simulants of: amber, copal, coral, ivory, jet, tortoiseshell; pearls — natural, cultured (nucleated and non-nucleated), marine and freshwater; shell (particularly as used for cameos and as mother-of-pearl).

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It is the kind of thing that would be wonderfully rewarding for high school seniors (or junior acolytes in Atlantean Shrines of the Book) to be studying. 'Instead' of science, I suppose.

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