UNIT
10 Minerals and rocks
ROCKS
Natural Science 1. Secondary Education
7
UNIDAD
3 Rocks
UNIT
10
Natural Science 1. Secondary Education
Magmatic
rocks
Volcanic
Plutonic
Metamorphic
rocks
Foliated rocks
Non foliated rocks
Sedimentary
rocks
Detrital rocks
Non- detrital rocks
Basalt
Granite
Slate Gneiss
Marble Quartzite
Conglomerates Sands Clays
Limestone Gypsum
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UNIDAD
3 Rocks
UNIT
10
Natural Science 1. Secondary Education
MAGMATIC VOLCANIC ROCKS
Pumice
Appearance
Grey or cream coloured rock, very light and
porous (it even floats in water).
Form in which it appears in nature
In accumulations of fragments (pyroclasts)
formed from pieces of lava spewed out by
the volcano and which solidifies in the air.
Composition
Silicates.
Texture
It is a porous mass in which the minerals
are not crystallised, so it does not have
grains.
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7
UNIDAD
3 Rocks
UNIT
10
Natural Science 1. Secondary Education
PLUTONIC MAGMATIC ROCKS
Granite
Appearance
White or pink coloured, compact rock with
black and orangey flecks.
Form in which it appears in nature
In large, rounded masses or in
accumulations of rounded rocks.
Composition
Potash feldspar, quartz and mica (biotite).
Texture
It has numerous grains, strongly bound
together, which are highly visible and very
uniform in size.
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7
UNIDAD
3 Rocks
UNIT
10
Natural Science 1. Secondary Education
FOLIATED METAMORPHIC ROCKS
Slate
Appearance
Black or dark brown coloured rock
composed of superimposed sheets.
Form in which it appears in nature
In layers, in flattened sheets which look
like pastry.
Composition
Quartz and muscovite (mica), resulting
from the metamorphism of the minerals of
the clays from which they proceed.
Texture
Superimposed laminar grains aligned in
the same direction.
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7
UNIDAD
3 Rocks
UNIT
10
Natural Science 1. Secondary Education
FOLIATED METAMORPHIC ROCKS
Gneiss
Appearance
Grey coloured rock with marked alternating
dark and light bands.
Form in which it appears in nature
In large layers, which are often sharply
folded.
Composition
Quartz, feldspar and micas.
Texture
Minerals arranged in bands with
occasional inclusions between them of
large grains of feldspar.
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7
UNIDAD
3 Rocks
UNIT
10
Natural Science 1. Secondary Education
NON-FOLIATED METAMORPHIC ROCKS
Marble
Appearance
White, cream or grey coloured rock, with
veins of very varied tones.
Form in which it appears in nature
In layers, between other metamorphic
rocks.
Composition
Calcite.
Texture
Large grains with no orientation or veins of
other minerals.
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7
UNIDAD
3 Rocks
UNIT
10
Natural Science 1. Secondary Education
NON-FOLIATED METAMORPHIC ROCKS
Quartzite
Appearance
Very compact rock with a white, cream or
reddish-brown colour.
Form in which it appears in nature
In very thick layers which often stand out
as enormous crests in the terrain due to its
great resistance to erosion.
Composition
Quartz.
Texture
Small grains of the original sandstone very
strongly held together by a cement which
is also of quartz.
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7
UNIDAD
3 Rocks
UNIT
10
Natural Science 1. Secondary Education
Conglomerate Appearance
Aggregate of pebbles cemented together.
Form in which it appears in nature
In layers.
Composition
Very varied; it depends on the rocks from
which the pebbles came and the type of
cement which holds them together.
Texture
Fragments of “gravel” type, held together
by a cement of finer grain. If the fragments
are rounded, the conglomerate is called
puddingstone; if they are angular, it is
called breccia.
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DETRITAL SEDIMENTARY ROCKS
7
UNIDAD
3 Rocks
UNIT
10
Natural Science 1. Secondary Education
DETRITAL SEDIMENTARY ROCKS
Sandstone
Appearance
Cemented aggregate of sand.
Form in which it appears in nature
In layers.
Composition
Depends on whether the sediments that
gave rise to it were quartz or sandstone, or
other rocks.
Texture
Grains of sand held together by a more
fine-grained cement.
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7
UNIDAD
3 Rocks
UNIT
10
Natural Science 1. Secondary Education
DETRITAL SEDIMENTARY ROCKS
Clay
Appearance
Rock with the appearance of dry mud,
whose colour varies from white through to
yellow, orange, red or grey.
Form in which it appears in nature
In layers.
Composition
Clay-type minerals such as kaolin and
other aluminium silicates.
Texture
Not very compacted microscopic
fragments.
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7
UNIDAD
3 Rocks
UNIT
10
Natural Science 1. Secondary Education
NON-DETRITAL SEDIMENTARY ROCKS
Limestone
Appearance
Compact rock of a white, grey or orangy
colour.
Form in which it appears in nature
In enormous, sometimes very thick series
of layers.
Composition
Calcite with some impurities.
Texture
Very fine grains of calcite, with occasional
inclusions of thicker grains. It often contain
fossils of marine creatures or is mainly
composed of their shells.
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7
UNIDAD
3 Rocks
UNIT
10
Natural Science 1. Secondary Education
NON-DETRITAL SEDIMENTARY ROCKS
Gypsum
Appearance
Not very compact, earthy, brown rock with
large white areas of gypsum.
Form in which it appears in nature
In layers.
Composition
Gypsum and cements of varied
composition, but generally limestone or
clays.
Texture
Large crystals of gypsum held together by
a fine-grained cement.
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