Note 112 — Chapter IV · The Microscopic and Optical Characters of Minerals. (continued 2)

In the determination of feldspar microlites it is well to remember the following facts: “Microcline is rarely, or never, seen in the condition of microlites, while the associations of labradorite and albite are so different that there is little danger of confounding them. Labradorite is the commonest product of the consolidation of the basic eruptives, and albite almost invariably results from metamorphism, frequently from the contact of igneous rocks on the calcareous clastics.” N. H. Winchell, Determination of the Feldspars, Am. Geol., Vol. XXI, No. 1, p. 33, 1898.