Quartz Limestone

A rock of only quartz and dolomite

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The rock in this image is essentially sand seen under the microscope, sand made up entirely of quartz. But unlike the sand that we find on beaches, this is a cemented rock, that is to say that the grains of sand 

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are held together by a natural cement that gradually deposited between the grains themselves as the sand was covered by other sediments.

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The grains of quartz are easy to distinguish in the photo. They are clear and colourful. But the cement is also clearly visible: it is made up of very small 

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dolomite crystals (a few hundredths of a millimetre) and appears as a veil of grey powder between the grains.

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This sand came from a hot and dry environment, from a river that evaporated so quickly that it never reached the sea.

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Geologists call these environments “dryland river systems”.  A similar environment can be found today 

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around Lake Eyre in Australia  Lago Eyre in Australia (28°2’20.00″S 137° 5’30.00″E) or at the foot of some mountains in the Arabian peninsula. (22°12’60.00″N 58°2’0.00″E).

Name: Quarzarenite
Classification: Clastic sedimentary rock
Mineral composition: Quartz, Dolomite, other
Fossils: None
Location: Dibona Refuse (46°32’5.09″N 12°4’21.20″E)
Formation: Travenanzes formation
Era: Upper Carnian (approximately 230 million years ago)
Depositional environment: Dryland river system