peridot, inclusions, gems

Gübelin gives a brief illustrated account of inclusions characteristic of peridot. He describes the internal features encountered in gem-quality olivine, emphasizing mineral inclusions and their diagnostic appearance under the microscope. Typical features of peridot include chromite and other spinel-group crystals, commonly surrounded by stress fractures or disc-like halos, as well as negative crystals and partially healed fractures. Such inclusions are useful both for identifying natural peridot and for interpreting aspects of its geological formation.