Mica sheets approximately 5 x 6cm, ~1mm thick.
Platy sheet crystal structure is clearly visible and crystal faces display typical uneven fracture.
These pieces of mica sheet have several layers and can be peeled to any thickness.
One layer can be peeled for a transparent sheet.
Gentle pressure with a scalpel against a steel ruler can be used to cut to the required size.
Mineralogy of Mica
For more information on mica: http://geology.com/minerals/muscovite.shtml