HALLEFLINTA (a

See also:

• SWEDISH

Swedish word meaning

See also:

• ROCK
• ROCK (O.Fr. rake, Sp. rota, Ital. rocca; possibly from a Lat. form rupica, from rupes, rock)
• ROCK, DANIEL (1799–187t)

rock-

See also:

• FLINT
• FLINT, AUSTIN (1812-1886)
• FLINT, ROBERT (1838- )
• FLINT, TIMOTHY (1780-1840)
• FLINT, or FLTNTSHTRE (sir Gallestr)

flint)  , a white, grey, yellow, greenish or pink, fine-grained rock consisting of an intimate mixture of quartz and felspar . Many examples are banded or striated; others contain porphyritic crystals of quartz which resemble those of the felsites and porphyries . Mica, iron oxides, apatite, zircon, epidote and hornblende may also be present in small amount . The more micaceous varieties form transitions to granulite and gneiss . Halleflinta under the microscope is very finely crystalline, or even cryptocrystalline, resembling the felsitic matrix of many acid rocks . It is essentially metamorphic and occurs with gneisses, schists and granulites, especially in the Scandinavian peninsula, where it is regarded as being very characteristic of certain horizons . Of its original nature there is some doubt, but its chemical composition and the occasional presence of porphyritic crystals indicate that it has affinities to the fine-grained acid intrusive rocks . In this group there may also have been placed metamorphosed acid tuffs and a certain number of adinoles (shales, contact altered by intrusions of diabase) . The assemblage is not a perfectly homogeneous one but includes both igneous and sedimentary rocks, but the former preponderate . Rocks very similiar to the typical Swedish halleflintas occur in Tirol, in Galicia and eastern Bohemia .