|Some opal is opaque and had no "fire". It is similar in appearance to some varieties of agate, but is lighter in weight. It is still heat sensitive and can be dehydrated causing cracking or discoloration. This stone cut by the author.
The word "dendritic" from "dendrite" describes the irregular branching line patterns found in the stone. This are cause by a secondary mineral depositing in small fissures or other secondary stress areas in the rough.