Hälleflinta (a
SwedishSwedish is a North Germanic language, spoken by approximately 10 million people, predominantly in Sweden and parts of Finland, especially along the coast and on the Åland islands. It is to a considerable extent mutually intelligible with Norwegian and to a lesser extent with Danish...
word meaning rock-flint), a white, grey, yellow, greenish or pink, fine-grained rock consisting of an intimate mixture of
quartzQuartz is the second most abundant mineral in the Earth's continental crust . It is made up of a continuous framework of SiO
4 silicon-oxygen tetrahedra, with each oxygen being shared between two tetrahedra, giving an overall formula SiO
2.There are many different varieties of...
and
feldsparFeldspars are a group of rock-forming tectosilicate minerals which make up as much as 60% of the Earth's crust....
.
Many examples are banded or striated; others contain porphyritic crystals of quartz which resemble those of the felsites and porphyries.
MicaThe mica group of sheet silicate minerals includes several closely related materials having highly perfect basal cleavage. All are monoclinic with a tendency towards pseudo-hexagonal crystals and are similar in chemical composition...
,
iron oxideIron oxides are chemical compounds composed of iron and oxygen. Altogether, there are sixteen known iron oxides and oxyhydroxides.-Oxides:* FeO, iron oxide, * Fe3O4, iron oxide,...
s,
apatiteApatite is a group of phosphate minerals, usually referring to hydroxyapatite, fluorapatite, chlorapatite and bromapatite, named for high concentrations of OH
−, F
−, Cl
− or...
,
zirconZircon is a mineral belonging to the group of nesosilicates. Its chemical name is zirconium silicate and its corresponding chemical formula is ZrSiO4. A common empirical formula showing some of the range of substitution in zircon is 1-x4x-y...
,
epidoteEpidote is a calcium aluminium iron sorosilicate mineral, Ca
2Al
2O, crystallizing in the monoclinic system. Well-developed crystals are of frequent occurrence: they are commonly prismatic in habit, the direction of elongation being perpendicular to the single plane of symmetry...
and
hornblendeHornblende is a complex inosilicate series of minerals . Hornblende is not a recognized mineral in its own right, but the name is used as a general or field term, to refer to a dark amphibole. It is an isomorphous mixture of three molecules; a calcium-iron-magnesium silicate, an...
may also be present in small amount. The more micaceous varieties form transitions to granulite and
gneissGneiss is a common and widely distributed type of rock formed by high-grade regional metamorphic processes from pre-existing formations that were originally either igneous or sedimentary rocks. Gneissic rocks are usually medium to coarse foliated and largely recrystallized but do not carry large...
.
Hälleflinta under the microscope is very finely crystalline, or even
cryptocrystallineCryptocrystalline is a rock texture which is so finely crystalline, being made up of such minute crystals, that its crystalline nature is only vaguely revealed even microscopically in thin section by transmitted polarized light. Among the sedimentary rocks, chert and flint are cryptocrystalline....
, resembling the felsitic matrix of many acid rocks.
Hälleflinta (a
SwedishSwedish is a North Germanic language, spoken by approximately 10 million people, predominantly in Sweden and parts of Finland, especially along the coast and on the Åland islands. It is to a considerable extent mutually intelligible with Norwegian and to a lesser extent with Danish...
word meaning rock-flint), a white, grey, yellow, greenish or pink, fine-grained rock consisting of an intimate mixture of
quartzQuartz is the second most abundant mineral in the Earth's continental crust . It is made up of a continuous framework of SiO
4 silicon-oxygen tetrahedra, with each oxygen being shared between two tetrahedra, giving an overall formula SiO
2.There are many different varieties of...
and
feldsparFeldspars are a group of rock-forming tectosilicate minerals which make up as much as 60% of the Earth's crust....
.
Many examples are banded or striated; others contain porphyritic crystals of quartz which resemble those of the felsites and porphyries.
MicaThe mica group of sheet silicate minerals includes several closely related materials having highly perfect basal cleavage. All are monoclinic with a tendency towards pseudo-hexagonal crystals and are similar in chemical composition...
,
iron oxideIron oxides are chemical compounds composed of iron and oxygen. Altogether, there are sixteen known iron oxides and oxyhydroxides.-Oxides:* FeO, iron oxide, * Fe3O4, iron oxide,...
s,
apatiteApatite is a group of phosphate minerals, usually referring to hydroxyapatite, fluorapatite, chlorapatite and bromapatite, named for high concentrations of OH
−, F
−, Cl
− or...
,
zirconZircon is a mineral belonging to the group of nesosilicates. Its chemical name is zirconium silicate and its corresponding chemical formula is ZrSiO4. A common empirical formula showing some of the range of substitution in zircon is 1-x4x-y...
,
epidoteEpidote is a calcium aluminium iron sorosilicate mineral, Ca
2Al
2O, crystallizing in the monoclinic system. Well-developed crystals are of frequent occurrence: they are commonly prismatic in habit, the direction of elongation being perpendicular to the single plane of symmetry...
and
hornblendeHornblende is a complex inosilicate series of minerals . Hornblende is not a recognized mineral in its own right, but the name is used as a general or field term, to refer to a dark amphibole. It is an isomorphous mixture of three molecules; a calcium-iron-magnesium silicate, an...
may also be present in small amount. The more micaceous varieties form transitions to granulite and
gneissGneiss is a common and widely distributed type of rock formed by high-grade regional metamorphic processes from pre-existing formations that were originally either igneous or sedimentary rocks. Gneissic rocks are usually medium to coarse foliated and largely recrystallized but do not carry large...
.
Hälleflinta under the microscope is very finely crystalline, or even
cryptocrystallineCryptocrystalline is a rock texture which is so finely crystalline, being made up of such minute crystals, that its crystalline nature is only vaguely revealed even microscopically in thin section by transmitted polarized light. Among the sedimentary rocks, chert and flint are cryptocrystalline....
, resembling the felsitic matrix of many acid rocks. It is essentially metamorphic and occurs with gneisses, schists and granulites, especially in the
ScandinaviaScandinavia is a geographical region in northern Europe that includes, and is named after, the Scanian Province. It consists of the kingdoms of Norway, Sweden, and Denmark...
n 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
TirolGerman Tyrol is a historical region in the Alps now divided between Austria and Italy. It includes largely ethnic German areas of historical County of Tyrol: the Austrian state of Tyrol and the Italian region known as the Alto Adige/Südtirol but not the largely Italian-speaking Trentino...
, in
GaliciaGalicia is a historical region in East-Central Europe, currently divided between Poland and Ukraine, named after the Ukraіniаn city of Halych. The nucleus of historic Galicia is formed of three regions of western Ukraine: Lviv, Ternopil and Ivano-Frankivsk.-Tribal area:The region has a turbulent...
and eastern
BohemiaBohemia is a historical region in central Europe, occupying the western two-thirds of the traditional Czech Lands, currently the Czech Republic...
.