Horse.

About Horse

A horse, in geology, is any block of rock completely separated from the surrounding rock either by mineral veins or fault planes. In mining, a horse is a block of country rock entirely encased within a mineral lode. In structural geology the term was first used to describe the thrust-bounded imbricates found within a thrust duplex. In later literature, the term became a general name for any block completely bounded by faults, whether the deformation is contractional, extensional or strike-slip in nature. Examples of horses have been described in both extensional duplexes and strike-slip duplexes.