a particularly interesting stone to try and write about because most of us are used to seeing it like this – chrysocolla mixed in with other minerals.
It commonly intergrows with chalcedony and can have a Mohs hardness of 4-7, depending on the percentage of chalcedony present. It also intergrows with malachite while Eilat stone is made up of a mixture of chrysocolla, malachite, turquoise and other minerals. It can also occur with other, different impurities, right up to the point where it is just present as a colouring agent… Interesting stone! But there’s more…
Gemstones are occasionally cut from its Caribbean blue, pure form… (I don’t have one in my collection I can photograph… yet!). Sadly, they only have a hardness of 2-4, their colour may fade and they are porous - all making them less suitable for use in jewellery. Although having said that, they can be impregnated with resin to improve their durability.
I’m afraid the challenge of trying to incorporate all this contrasting information in one of the quick reference tables in my jewellers' quick reference guide to working with gemstones caused a little brain melting moment so I decided not to include it… but here’s the information anyway!