Mica I dug from a site in Easton Pa.

This is the mineral Mica dug from a site I found in my home town.

The mica group of sheet silicate (phyllosilicate) minerals includes several closely related materials having close to perfect basal cleavage. All are monoclinic, with a tendency towards pseudohexagonal crystals, and are similar in chemical composition. The nearly perfect cleavage, which is the most prominent characteristic of mica, is explained by the hexagonal sheet-like arrangement of its atoms.
The word "mica" is derived from the Latin word mica, meaning "a crumb", and probably influenced by micare, "to glitter".