Gemology 101

Question 1

How does a gemstone get its colour?

Answer 1

A gemstone will absorb or reflect different colour wavelenghts depending primarily on the chemicals it contains.
Gemstones appear black when they absorb all colour
The colour wavelength(s) they don’t absort is reflected back, ie green in peridot

Question 2

Some gemstones in their chemically pure state don’t absorb any colour wavelengths. Provide an example

Answer 2

Beryl doens’t absorb any colour wavelenghts, therefore appears colourless to us.
HOWEVER, tiny impurities in a stone can cause some light to be absorbed rather than reflected and depending on the impurity we see green (emerald), blue (aquamarine), etc

Question 3

What is the role of an impurity in a stone?

Answer 3

Impurities can change the colour of the whole stone, as with beryls

Question 4

What is the role of an inclusion in a stone?

Answer 4

Inclusions are relatively large amounts of some foreign substance embedded in a gemstone.
Becuase the inclusion has a different chemical composition than the gemstone itself, it absorbs and reflects different colour wavelenghts than the gemstone does
Most inclusions are undesirable, but some can create effects like chatoyancy and asterisms