Καλημέρα.
Βρίσκω ένα silkstone στη Wikipedia, το binghamite, ένα είδος αχάτη, αλλά δηλώνω γεωλογικώς αναρμόδιος:
Binghamite (also called silkstone and cuyunite) is a type of agate stone found only on the Cuyuna iron range (near Crosby) in Crow Wing County, Minnesota. The formation of the stone occurs near deposits of iron ore.
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