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Engineering Geology/Rock identification


Would you please teach me some ways for identifying the rocks listed below? What equipments do I need for this purpose? I'm looking for the simplest ways.
Marble- granite- travertine- pumice- slate- alabaster- basalt- gypsum- dolomite- ecaussine- porphyry- sandstone- stealite

Identification of a rock is a subject taught in Geology. It requires knowledge of composition (mineral constituents), color, texture, cleavage etc. of the rock for  its proper identification.

A pocket lens ( magnification 10x ) is necessary for study of rock in hand specimen. Thin section study of rock is done under petrological microscope for finding the mineral constituents, texture etc. of the rock towards its identification including its name.

The identification approaches of the mentioned rocks are stated below in short:

Marble -  It is the metamorphic equivalent of limestone consisting mainly of calcium carbonate with some magnesium carbonate. It is a very dense rock that occurs in various colors depending upon constituent impurities. The rock can be scratched by a knife and when dilute hydrochloric acid is poured on rock powder, it will show effervescence.

Granite - is an igneous rock white to light pink in color. It consists of felspar (mainly orthoclase, also plagioclase, microcline etc.), quartz and ferromagnesian minerals. The color of the felspar mainly decides the color of the rock.

Travertine - is a sedimentary rock of low porosity and low sorption showing laboratory test results on 3 samples as porosity (2.63%) and sorption (1.07%).

Pumice - is a light colored volcanic rock of glassy texture. The rock occurs as surface flow of lava.

Slate - is a dark colored fine grained metamorphic rock with closely packed foliation and well developed cleavage along which the rock splits easily.

Alabaster - It is a dense granular form of gypsum composed of hydrous calcium sulphate, quite soft and occurs in white, grey and pink color and used in carving.

Basalt - Fine grained dark colored volcanic rock, generally glassy and vesicular in texture

Gypsum -   It is a soft mineral consisting of calcium sulphate that can be scratched by a finger nail.

Dolomite - It is a soft mineral composed of magnesium sulphate.  It can be white, grey, brown and pink in colour. When hydrochloric acid is poured on its powder, It causes effervescence.

Porphyry - It is an igneous rock with coarse texture. Study of thin section of rock under microscope shows some large crystals embedded in fine textured matrix.

Sandstone - It is a fine, medium or coarse grained sedimentary rock consisting mainly of quartz and also of felspars and other minerals in subordinate quantity.

Hope this helps. For more details, refer to any basic geology book or also my book which is a bit advanced but can help to some extent. It is available on Oxford University Press:

Engineering Geology

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Subinoy Gangopadhyay


1. All questions related to Engineering Geology. 2. Geo-Technical aspects of engineering geology projects of India. 3. Any other Geology related questions.


I served for a period of 34 years in the engineering geology division of Geological Survey of India (GSI) advising on Geo-Technical aspects of more than hundred civil engineering projects in India and abroad. I retired as Senior Director from GSI. I have a Ph D in Engineering Geology. I am also a founder member of Indian Society of Engineering Geology and served as the editor and Vice President of this Society. I have written nearly 150 technical reports on Geo-Technical aspects of engineering projects of India including some projects abroad where I worked as a consultant. I have published numerous technical papers in reputed national and international journals.

Geological Survey Of India (GSI) Indian Society of Engineering Geology (ISEG)

Recently authored a text book for Engineers and Geology students pursuing Bachelors, Masters and Doctoral studies in Civil Engineering, Geology and Mining Engineering areas. The book has been published by Oxford University Press and is also available on Amazon: Also published books on Monuments of India - Volumes 1 & 2, available on Amazon:

M.Sc. in Geology from Presidency College, Calcutta. Ph D in Engineering Geology from Calcutta University, Calcutta.

Awards and Honors
Presidents Gold Medal winner for the best paper published in Geological and Mining Society of India, 1965.

Past/Present Clients
Geological Survey of India, Kolkata. Lega Dembi Gold Mine, Ethiopia. Sonatrach Oil, Gas and Petroleum, Algeria. Geotechnical Testing, UNO, Tanzania. Norwegian Geotechnical Institute, Norway.

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