Aventurine

Aventurine is most often thought of as being green, but also occurs in blue, orange and red. All varieties of aventurine are types of chalcedony (agate). There are over thirty distinct varieties of agate making it one of the largest families of stones. All agates are composed of SiO₂ They form according to a trigonal crystal structure, and have a hardness of 7 on the Mohs scale.