Gemmology
- 1. Gemmology Welcome to the fascinating topic of Gemmology, the science of natural and artificial gemstones. It falls under the discipline of geo-science and mineralogy. Danny Evans Assessment 3 SCI102
- 2. What is a Gemstone? By modern definition, a gemstone is a mineral or other natural material that is beautiful enough, durable enough, and rare enough, to be used for personal adornment or for the embellishment of personal possessions.
- 3. Which gem is this? With such a large variety of gemstones and valuable minerals, it is easy to confuse one stone for another. Contrary to popular belief, gems do not have a set colour, this is due to differences in mineral composition. These are ALL Sapphires.
- 4. So how can we identify a Gemstone ? Nearly 300 variations of diamond colour exhibited at the Aurora display at the Natural History Museum in London. Due to scarcity of information, I had to resort to using Wikipedia information.
- 5. Identification by Refractive Index One test to determine the gem's identity is to measure the refraction of light in the gem. Every material has a critical angle, at which point light is reflected back internally. This can be measured and thus used to determine the gem's identity. Typically, this is measured using a refractometer although it is possible to measure it using a microscope. Refractometer
- 6. Identification by Specific Gravity Specific gravity, also known as relative density, varies depending upon the chemical composition and crystal structure type. Heavy liquids with a known specific gravity are used to test loose gemstones. Specific gravity is measured by comparing the weight of the gem in air with the weight of the gem suspended in water.
- 7. Identification by Spectroscopy This method uses a similar principle to how a prism works to separate white light into its component colours. A gemmological spectroscope is employed to analyse the selective absorption of light in the gem material. Essentially, when light passes from one medium to another, it bends. Blue light bends more than red light. Depending on the gem material, it will adjust how much this light bends. Colouring agents or chromophores show bands in the spectroscope and indicate which element is responsible for the gem's colour.
- 8. In Conclusion Thank you for following along with the presentation, hopefully you will have gained insight into Gemmology. Next time you find a gemstone, try to find out what it is. You may be surprised. For more information, check the Gemmological Association of Australia at http://www.gem.org.au