Bostonite, in petrology, is a fine-grained, pale-colored, grey or pinkish intrusive rock, which consists essentially of alkali-feldspar (orthoclase, perthite, anorthoclase, and albite).
Accessory minerals include chlorite, apatite, zircon and magnetite, with rare biotite, hornblende or pyroxene.
[1] These rocks are characterised by a 'bostonitic' texture of clusters of subparallel, divergent or radiating irregular feldspar laths in a fine grained matrix.
Though nowhere very common they have a wide distribution with occurrences in Scotland, Wales, Massachusetts, Ontario, Portugal, Bohemia, and other places.
[1] The term was widely used in the geologic literature of the late 19th and early to mid 20th centuries, but is currently being discouraged in petrologic usage.