Elaterite

Elaterite, also known as Aeonite, 'elastic bitumen' or 'mineral caoutchouc'.

Elaterite is a brown hydrocarbon varying somewhat in consistency, being sometimes soft, elastic and sticky, like India rubber, and occasionally hard and brittle. It is usually dark brown in color and slightly translucent. A substance of similar physical character is found in the Coorong district of South Australia, and is hence termed coorongite. It is said to be carcinogenic.