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In biotite hornfelses a faint striping may indicate the original bedding of the unaltered rock and corresponds to small changes in the nature of the sediment deposited.

The snowy white feldspar and quartz set off the glittering crystals of hornblende and biotite wonderfully.

The biotite is brown; the hornblende brown or greenish brown; the augite usually green.

The commonest accessory minerals are tourmaline, topaz, apatite, fluorspar and iron oxides; a little felspar more or less altered may also be present and a brown mica which is biotite or lithionite.

Exceptions to this sequence are unusual; sometimes the first of the felspars have preceded the hornblende or biotite which may envelop them in ophitic manner.