This document introduces gemmology, the science of natural and artificial gemstones. It discusses what qualifies something as a gemstone, noting that gemstones must be beautiful, durable, and rare enough for personal adornment. The document then explains several methods used to identify unknown gemstones, including measuring the refractive index, specific gravity, and using spectroscopy to analyze light absorption. In conclusion, it encourages learning more about identifying gemstones.

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

9. Reference List
http://collectionphotos.com/latest-gemstones-hd-pictures-2014/
http://en.wikipedia.org/wiki/File:Gem.pebbles.800pix.labelled.jpg
http://www.gem.org.au/the-resources/faqs/
http://en.wikipedia.org/wiki/Sapphire
http://en.wikipedia.org/wiki/Gemology
http://en.wikipedia.org/wiki/File:Aurora_Diamond_Collection.jpg
http://www.gem.org.au/