When I bought these stones, the sales tag said they were green amethyst, but I knew better. They are prehnite and quite recognizable by the rutiles (the black lines) within the faceted gems. Rutilates, or shards of mineral, can show up in any number of stones. Golden rutilated quartz has shards of gold in them and is very pricey. These beads were a very fair price and with their faceted, they have quite an un-earthly glow to them. I mixed them with deep ebony Swarovski crystal and finished them off with a sterling silver clasp.