Note 110 — Chapter IV · The Microscopic and Optical Characters of Minerals.

For this method of investigation little cleavage flakes or plates can often be obtained from the crushed mineral, but, on account of Albite twinning, plates are more apt to be obtained parallel to the twinning plane than to the best basal cleavage. If a fragment with only one cleavage surface is obtained, it must be cemented to a glass by this surface and ground down to a thin section with parallel sides.