SYLLABUS D-GEM

Syllabus for the Diploma in Gemmology Examination by GASL ...

01. Gem materials.

Introduction. Gemmology as a science. Related subjects covered in the study of gemstones. What includes as gem materials and ornamental materials. Nature and attributes of gems and ornamental materials. Factors which influence the value of gemstones. Beauty, durability, rarity and acceptability.

02. Geology related to gem minerals.

The Earth's structure and the geological activities.
The Origin and occurrence of gem minerals.
Major types of gemstone occurrences- Pegmatite deposits, Diamond volcanic
deposits, Hydrothermal deposits, Placer deposits.
Extraction: mining and recovery methods (outline only)
Gem mining and extracting methods in Sri Lanka.

03. Chemical 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.

04. Crystallography related to gem materials

The nature of crystals; crystalline materials.
Crystals and polycrystalline (including microcrystalline) materials.
The relationship of crystal structure and symmetry to crystal faces, forms, habits, cleavage, internal growth phenomena and crystal surface markings; relevance to identification A basic understanding of the following: reference (crystallographic) axes; crystal symmetry; crystal form; crystal habit; twinning.
The seven crystal systems: the reference (crystallographic) axes for each system; symmetry essential and important to each of the systems; common and typical crystal forms for crystals in each of the systems.
Amorphous and metamict materials; Crystalline features in some important gemstones- apatite, beryl, corundum, diamond, fluorite, garnet, topaz, quartz, pyrite, tourmaline and zircon

05. Physical properties of gemstones Specific Gravity

Density and specific gravity (SG). Definitions of density and SG.
SG measurement and hydrostatic weighing: Archimedes' principle.
The use of high-density liquids in gem testing; care and caution in use.

06. Durability of Gem Materials

Hardness: definition and significance; testing and Mohs' scale; differential hardness.
Toughness and stability. Fracture; types of fracture.
Cleavage: definition, description and significance. Parting.

07. Optical Properties

The importance of light in gemmology. The electromagnetic spectrum. Wavelength and frequency.
The nature of visible light. The visible spectrum of colour.
Optical properties of crystalline and non-crystalline gem materials.
Polarization and vibration direction.

08. Transparency, Reflection and Dispersion

Transparency, its degree as an observation for gem identification, cutting and grading Reflection and its Effects External reflection: lustre. Examples of lustre.
Total internal refeaction and the results Brilliance.
Dispersion of light in gemstones. Its production and results in gemstones. Its measurement Observation of optical results from dispersion in appreciation for beauty, and gemstone identification.

09. Directional optical properties. Optical behaviour in gemological instruments

The systematic interaction of light with crystal structures: Isotropic and anisotropic qhality, pleochroism, polarization, optic axes and optic axial interference figures; uses in gem testing.

10. Polarized Light; the Polariscope

The nature of polarized light. Isotropic and anisotropic behaviour; optic axes.
The production of polarized light; the polarizing filter; 'crossed' polarizing filters. The polariscope: construction and use; typical results;

11. 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, construction; the principle of total internal reflection.
The determination of birefringence and optic sign: their measurement by refractometer and by other methods.

12. Colour; the Visible Spectrum

Light and body colour in gemstones. Dispersion, 'fire' and diffraction.
Body colour and selective absorption of light.
Colouring elements; allochromatic and idiochromatic materials.
Colour and its causes in gem materials; luminescence; diamond types.
Pleochroism; the dichroscope, construction and use; typical results.

13. Physical optics; optical phenomena that affect light -

Internal reflection effects caused by regular inclusions or structural features.
Special optical effects caused by inclusions; chatoyancy and asterism Special optical effects caused by interference and diffraction

Internal reflection effects caused by regular inclusions or structural features. Special optical effects caused by inclusions; chatoyancy and asterism Special optical effects caused by interference and diffraction

14. The absorption spectrum and the spectroscope.

Optical spectroscopy.
Construction and function of the two types of spectroscope.
The absorption spectra of the following materials:

Apatite,
almandine garnet
chrysoberyl,
alexandrite,
emerald,
enstatite
peridot,
Sinhalite,
ruby,
blue sapphire,
Blue spinel,
red glass (selenium),
red glass (gold),
blue glass (cobalt),

blue Verneuil synth. spinel (Co) zircon,
Use of colour filters; the Chelsea colour filter.
Colour change effect ('alexandrite effect').

15. Non-visible Radiation, Energy and Fluorescence

Luminescence: fluorescence and phosphorescence Use of the ultra-violet lamp (short wave and long wave).
The use of X-rays in gemmology.
Thermal conductance and electrical conductivity probes; reflectance meters.

16. General study of the advance analytical methods in gem testing

A broad knowledge of the gem testing techniques employed in gemmological laboratories; Use of advance instruments related to the functions of infrared, ultraviolet and X-rays.

17. Optical Magnification

Magnification Techniques; Internal and External Features Magnification: the 10x lens and the gemological microscope; Lighting methods used in observations under optical magnification.
Observation of gem materials: internal features, external features and the study of inclusions, in rough and fashioned natural, artificial, treated and imitation gem materials.;
immersion of gems to aid observation.

18. Thermal conductance and electrical conductivity probes;

Thermal properties and the uses of thermal conductance Related meters in gem identification probes in gem testing.
Electrical properties of gem materials.

19. Description and Methods of Identification of Natural Inorganic Gem Materials under the following subheadings.

Chemical composition. Crystal system and crystal habit. Characteristic crystal face markings and features Common and characteristic crystal forms, and crystal face markings and features.
Cleavage and fracture.
Hardness.
Specific gravity.
Colour; causes of colour; pleochroism. Lustre.
Internal reflection effects (including iridescence, chatoyancy and asterism); Refractive index (with birefringence).
Birefringence with optical nature and optic sign Dispersion (description of relative amounts only).
Common and characteristic inclusions.
Absorption spectra Luminescence Separation of gem materials from their synthetics and most common simulants Major geological occurrences.
Major world localities of commercial deposits.
The materials include the following; Beryl, corundum, garnet, quartz (including chalcedony), chrysoberyl, iolite, spinel, jadeite, tanzanite, diamond, nephrite, topaz, feldspar, opal, tourmaline, fluorite, peridot, zircon.

20. Additional Gem Materials

The most important distinguishing features of the following materials: Andalusite, apatite, calcite (Iceland spar; banded and massive ornamental varieties; marble), diopside, fluorite, glass - natural and artificial, (including obsidian and moldavite), gypsum (including alabaster), hematite, hydro-grossular garnet, lapis- lazuli, malachite, pyrite, rhodochrosite, rhodonite, scapolite, serpentine (including bowenite), sinhalite, sodalite, sphene, spodumene, steatite (soapstone), turquoise, steatite, cubic zirconia (CZ), synthetic moissanite, synthetic rutile, strontium titanite, turquoise

21. 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). The formation and structure and methods of identification of natural and cultured pearl. An elementary knowledge of the formation, properties and methods of identification of:

22. Units of measurement essential to this course and examination:

metric carat (ct) metre (m) litre (l)
pearl grain millimetre (mm) millilitre (ml)
kilogram (kg) micrometre (µm) cubic centimetre (cc)
gram (g) nanometre (nm)
milligram (mg) temperature (°C)

23. Artificial Gem Materials

Artificial and synthetic gems: definitions. Single-crystal growth of artificial materials; nucleation;
An outline of methods of production and identification of materials produced by the Verneuil flame-fusion, flux melt and hydrothermal. skull melting process for cubic zirconia;
Czochralski 'crystal pulling' method; 'floating zone' (zone melting) method; high pressure high temperature synthesis of diamond

Methods of production for Y.A.G., synthetic rutile, strontium titanite and synthetic moissanite.

24. Non-crystalline artificial materials: paste; plastics.

A brief outline of the production methods/manufacture of synthetic opal, turquoise, lapis lazuli, coral composite (assembled) materials and reconstructed materials.

25. 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.

Composite (assembled) natural and artificial stones; reconstructed materials.

26. Treated Gem Materials

Examples of methods of treatment (enhancement) and their identification, including dyeing, bleaching, impregnation, coating, irradiation and annealing, heating, laser treatment, fracture filling and diffusion treatment.
Special description on heat treatment and diffusion methods HPHT diamond treatment.
Disadvantages and advantages of treatment or enhancement. (Descriptions, identification, detection: item

27. Fashioning of Gemstones

General description of fashioning of gemstones Description of gemstone cuts: specifically the brilliant (with proportions for round brilliant-cut diamond); step (emerald) cut; mixed cut; cabochon cut.
A brief description of other common cuts.
Reasons for the use of various cuts.
Processes in lapidary and diamond manufacture.

28. Valuation and marketing

Appraisal and valuation. Valuation standards of gemstones,
Gemstone appraisal procedures.
Marketing of gemstones and Export procedure.

29. Gems in jewellery

Gem settings in jewellery. Gem identification and diamond grading reports. Testing gems in jewellery.

30. Trading procedure in the internal trade in Sri Lanka and the export procedures.

Regulations related to trading, exports, mining, lapidary activities, diamond manufacture, Jewellery making etc.