Chlorite Family

Chlorite, a basic iron magnesium aluminum silicate, is most often associated with low and medium temperature metamorphic rocks. It's a name for a group of 10 similar minerals in the micaceous phyllosilicate formation, members of the silicate family. 

Chlorite is very common, and often is an uninteresting green mineral coating the surface of other minerals. However, there are some crystal forms and varieties that are attractive on their own right  or as inclusions like chlorite included quartz.