page_title: Halleflinta
hierarchical_section_title: Halleflinta
caption_attribution_description: Svenska: Upplands landskapssten är den täta, finkristallina hälleflintan. Trots sina likheter med flintan har hälleflintan ett helt annat ursprung. Ursprungligen, för ca 1900 miljoner år sedan, avsattes den som vulkanaska. Hälleflintan är nästan alltid tydligt randig, i färger som gråsvart-olivgrå-rödvit-svartgrön-gulbrun. Den förekommer ofta växellagrad med urkalksten och metallmineraliseringar. Hälleflintan användes under stenåldern till redskap i flintfattiga områden, särskilt i norra Skandinavien. Den har brutits i liten skala för framställning av ställsten för infodring av masugnar. English: Halleflinta from Uppland in Sweden. The rock was formed about 1900 million years ago as volcanic ash. Halleflinta almost always has a striped appearance. Colours include grey, black, red, white, green, yellow or brown.
context_page_description: Hälleflinta, a white, grey, yellow, greenish or pink, fine-grained rock consisting of an intimate mixture of quartz and feldspar.
  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.
  Hälleflinta 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. The assemblage is not a perfectly homogeneous one but includes both igneous and sedimentary rocks, but the former preponderate.
context_section_description: Hälleflinta (a Swedish word meaning rock-flint), a white, grey, yellow, greenish or pink, fine-grained rock consisting of an intimate mixture of quartz and feldspar.
  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.
  Hälleflinta 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 similar to the typical Swedish hälleflintas occur in  Tirol, in Galicia and eastern Bohemia.
   This article incorporates text from a publication now in the public domain: Chisholm, Hugh, ed. (1911). "Hälleflinta". Encyclopædia Britannica. 12 (11th ed.). Cambridge University Press. p. 855.
caption: Hälleflinta
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