It is a variety of quartz that can be translucent or opaque with various colours: Carnelian if it is orange, Chrysoprase if it is green, Onyx if black.

 SOME HANDMADE JEWELS MADE WITH AGATE BY SARTORI ITALIAN JEWELLERY:

ART. TS016 Silver necklace with fresh water pearls, chalcedony and citrine

 Gioielleria Sartori gioielli artigianali 

Grosseto - Italia