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A fine-grained, light-colored igneous rock, composed chiefly of feldspar and quartz.

fel·sit′ic (-sĭt′ĭk) adj.
American Heritage® Dictionary of the English Language, Fifth Edition. Copyright © 2016 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.
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In the related, banded, albite-rich felsitic schist, the light bands are composed of fine-grained albite, calcite, chlorite (Mg# = 0.85-0.89), and amphibole.
Minor grain types include chalcedonic microcrystalline quartz of indeterminate origin but possibly from amygdules in volcanic rock, polycrystalline microlitic and felsitic volcanic rock fragments (in addition to more abundant glassy volcanic rock fragments), equant opaque iron oxide grains that are probably magnetite, internally foliated fragments of metamorphic slate, and rare aggregate epidote grains.
The property is underlain by a northeast striking belt of basic intrusive and extrusive rocks intercalated with metasedimentary rocks and intruded by quartz feldspar porphyry and felsitic rocks.