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dear sir i like you ans sir please give me 2 more ans thanks

my question is
a.what the difference between silt and siltstone we identify silt and siltstone in the field

a.what the difference between sand and sandstone we identify sand and sandstone in the field

Wentworth scale chart
Wentworth scale chart  
Dear Arman Khan,

The rock grain size measurement scale was published by Chester K. Wentworth in 1922 by , modifying an earlier scale by Johan A. Udden. Wentworth's grades and sizes were later supplemented by William Krumbein's phi or logarithmic scale, which transforms the millimeter number by taking the negative of its logarithm in base 2 to yield simple whole numbers.

I am sure you know that gravels (boulders, cobbles, pebbles and granules) are coarse grained sediments followed by sand, silt and clay. These  are broken pieces found in nature and their origin has been  other preexisting sedimentary or other rocks (metamorphic and igneous)and are also known as clastic detritus. When these loose sediments solidify due to compaction and cementation a hard and solid rock is formed.

Most coarser rock fragment is boulder which has a diameter of more than 4096mm, followed by other lesser coarse grains. The size of the coarse sand is about 1mm with reducing size down to the level when grain size reduces to 0.625 mm. The silt is the rock particle size less than 0.625mm. You can say that silt is the most finest sand particle.

In the field you can use Wentworth scale card to measure the silt and sand size under the microscope or use field lens when micrscope is not available. When I used to do the mudlogging our logging unit was always supplied with Wentworth scale which was very handy and I used to select and put  few grains on the Grain scale chart and try to differentiate between sand, silt and clay on the basis of grain size.

There is a mechanical method to classify sand, silt and mud grade off the rock. This method is known as particle size analysis and involves the grinding of the rock and passing the grains through 2 mm mesh sieve and later through finer mesh sieves.

Other precise way to differentiate siltstone with fine sandtstone is to prepare thin section of the fragment of the rock and examine under the electron microscope or  polarized microscope.

Silt and sand are loose grains and when solidify due to compaction and cementation they become rock and known as sandstone and siltstone.

Hope, this answer will be helpful.

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Syed Tariq Hasany




Petroleum Exploration

Petronas Carigali Sdn Bhd

In Pakistani and Asian Petroleum Confertence special Publications

BSc Honours in Geology and Master of Science degree in Petroleum Geology

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