DDG Ass #18 Key Terms and Concepts PDF

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ComplementaryLutetium

Uploaded by ComplementaryLutetium

Gemological Institute of America

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gemstones diamond simulants geology

Summary

This document describes key terms and concepts related to identifying gemstones, particularly diamond simulants. It covers various aspects such as doublets, electrical conductivity, and different types of simulants like paste and rhinestones.

Full Transcript

DDG Ass #18 Key Terms and Concepts Doublet—Two pieces of material fused or cemented together to form a single assembled stone. Diamond Simulant—Any material that is not natural diamond or lab-grown diamond, but imitates a diamond’s appearance and is used in its place. Electrical Conduct...

DDG Ass #18 Key Terms and Concepts Doublet—Two pieces of material fused or cemented together to form a single assembled stone. Diamond Simulant—Any material that is not natural diamond or lab-grown diamond, but imitates a diamond’s appearance and is used in its place. Electrical Conductivity—A measure of how well an electrical current passes through a material. Foilback—A gemstone or simulant with a thin metallic foil or mirroring film applied to its pavilion. Heft—How heavy an object feels in relation to its size. Multi-Testers—An instrument that measures both thermal and electrical conductivity to test diamonds and simulants. Paste—Glass imitation gemstones and diamonds. Rhinestone—A trade term used to describe diamond imitations made of glass or plastic, with or without foilback. Subadamantine—Surface appearance with slightly less sharp reflections than adamantine. Thermal Tester—An instrument that measures thermal conductivity to help separate natural and lab- grown diamonds from most simulants. Vitreous—Glass-like surface appearance. Key Concepts: Simulants can be natural or human-made. Simulants can be produced in nearly any size and quantity and cost less than natural or lab-grown diamonds. Convincing diamond simulants mimic diamond’s features. No simulant mimics all of diamond’s features. Diamond simulants have improved over time, but older simulants may still be seen. Synthetic and natural colorless sapphire were popular diamond simulants in the 1990s. Zircon and cubic zirconia are two different simulants. CZ is the most popular diamond simulant on the market. To identify assembled simulants, pay special attention to luster differences and the area just above and below the girdle. To identify color coatings on simulants, pay attention to facet junctions and oily or iridescent facets under magnification. A combination of methods is needed to conclusively identify a stone. Diamond has a higher thermal conductivity than most simulants. Synthetic moissanite can cause a standard diamond tester to indicate diamond. Moissanite testers use electrical conductivity to separate synthetic moissanite from diamonds and other simulants. Make sure to check for doubling in at least three directions. The read-through test is only reliable for well-proportioned round brilliant cut stones. The heft test only works for loose stones. Diamonds have a lower SG and lower heft than most simulants. Subadamantine and vitreous are the best lusters simulants can show. Girdles on simulants can’t be bruted like those on diamonds. A jewelry professional can help clients or customers feel good about buying simulants. Be aware of trade names and misnomers for common diamond simulants. Do not sell a gem unless certain of its identity. The best defense against false claims about simulants is thorough knowledge and up-to-date skills.

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