Norm ASTM D2131-97R03
1.1 This specification covers the determination of muscovite mica splittings of standard commercial grades and specifies the maximum allowable physical defects for each grade. It is applicable to commercially available natural muscovite mica splittings regardless of the basic color of the mica or its source.
1.2 The values stated in inch-pound units are to be regarded as the standard. The values given in parentheses are for information only.
1.3 This standard is very similar to ISO 6386. It is expected that materials would be classified identically using the criteria of either standard. The grades shown under "ASTM Grade No." in Table 1 and Table 2 are shown under "Old Grade No." in ISO 6386.