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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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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7