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My son found this stone on the beach on the island Crete. It was a one of its kind, no other visible stone on the beach was the same.
We asked the locals, but they did not know this stone.

It's about 15 cm long and weighs 1,3 kg.
It's not very hard or soft. I think it is a litle harder than marble: I can scratch it with a knife, but just barely, a coin can not scratch it.

Is it marble?
Where does it originate from?

picture of the stone

closeup

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    $\begingroup$ you are on to a good start in describing it but take a look here earthscience.meta.stackexchange.com/questions/124/… and try to add more information, the more you can tell about it the better the answer will be.maby do the acid test on a tiny part of the rock. $\endgroup$ – trond hansen Mar 29 '18 at 15:22
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Your rock is most likely a blue-schist metamorphic rock.

From Wikipedia: Blue-schist

Blueschist ( /ˈbluːʃɪst/), also called glaucophane schist, is a metavolcanic rock1 that forms by the metamorphism of basalt and rocks with similar composition at high pressures and low temperatures (200 to ~500 degrees Celsius), approximately corresponding to a depth of 15 to 30 kilometers. The blue color of the rock comes from the presence of the predominant minerals glaucophane and lawsonite.

Blueschists are typically found within orogenic belts as terranes of lithology in faulted contact with greenschist or rarely eclogite facies rocks

Science Digest: Blue-schist Crete has well studied blue-green schist metamorphic lithologies.

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  • $\begingroup$ Indeed a blueschist, and a marvellous example of one! $\endgroup$ – Gimelist Mar 30 '18 at 14:32

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