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How To Tell the Difference Between Coal and Jet

Jewellery & Watch News



Whitby Jet has many lookalikes with coal being one of them. The two are very similar and to an untrained eye it can be very difficult to tell the difference between coal and Whitby Jet. Our beaches are inundated with black fragments making it nearly impossible for gem hunters to stumble across the real deal. From charcoal left over from indulgent beach bbq’s to black plastic, many believe the lookalikes to be genuine Whitby Jet. To be honest, it is hard to distinguish between the two however, there are a few ways to know if you’ve uncovered an authentic piece or are in fact holding a piece of coal.

Although very alike in appearance how they are formed is very different. Jet is fossilised wood that has formed under very specific conditions and coal is a sedimentary rock that contains fossilised plants. 


The Smudge Test - an easy way to tell the difference is to make a mark on a piece of wet/dry paper or unglazed porcelain. Jet will leave a light brown streak whereas coal’s mark is black when rubbed on a ceramic tile for example. 


The Touch Test - to put it simply Jet is warm to touch while coal is cold. Therefore, when holding the piece of Whitby Jet it will be surprisingly warm in your hand. 


The Brittle Test - Jet is much harder than its copycat and coal will crumble much easier as it is very brittle.  


The Colour Test - wet coal does look very similar to Jet however, when dry it is more of a grey colour and has layers that are either dull or shimmer. Jet is a definite black and never sparkles. 


We won’t complicate things, all you need is these four simple tests to help you distinguish between coal and Jet. If still unsure, asking a professional is always a good idea. 


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