Importance of Geology in Rock Monuments

1. Importance of Geology in Rock Monuments
Dr Vadagbalkar S.K.
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Importance of Geology in Rock Monuments
Abstract:
The Indian monuments are the living examples which take us back to
thousands of years and helps in exploring the history of India. These monuments-
dominated by Megalithic structures - which are in large stone that has been used to
construct a structure or monument, either alone or together with other stones, utilizing
an interlocking system without the use of mortar or cement. Rocks that can stand the
ravages of time and weather, those that possess the requisite strength, homogeneous -
or monolithic nature, compact- hard with fine grains, an attractive colour and
appearance, and most important is their dressing character, are the most valuable
factors considered in the past for selection of construction and carvings of
archaeological monuments and structures. Combined with natural hazards, weathering
process, climate conditions, and topography etc. has either destroyed completely or
left these monuments as partial ruins.
Keywords- Carvings, Geological weathering, Megalithic, Stone Monument
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Introduction:
The earliest phase of Indian architecture may be seen from the remains of the
ancient cities of the Indus Valley culture datable to c. 3000 B.C. Materials for
sculpture can be just stone, bronze, clay and durable wood in case of India. Most of
these materials are long lasting materials. It is based on the fact, the varieties that was
available in plenty of manner in particular region was used for the art. Metal used can
be ranged as per the quality and resistance.
There is no doubt that the purpose of creating sculpture has been to create a
piece of art that should be permanent as far as possible. Therefore, with that aim the
work was usually produced in durable and frequently expensive materials, primarily
Bronze. Very rarely precious materials such as gold, silver, jade and ivory were used
for preparing art works. But more common, mostly preferred and less expensive
materials that was used for producing sculpture on wider scale are stone & wood. The
architecture of the Asokan period (c. 273-237 B.C.) gains in magnificence, as for the
first time stone was employed instead of wood. The general sequence is as follows:
1) Harappan culture`s sculpture was made mainly from clay material, probably due to
easy availability in surrounding( agriculture man) and understanding its casting-
molding capacity.
2) Then there was a boom of creating wooden sculpture. People were used it for
houses and in the temples. Examples are the statue of Sun in Multan, statue of

2. Importance of Geology in Rock Monuments
Dr Vadagbalkar S.K.
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Lord Jagdish in Jaganathpuri and Rannadevi`s statue in the Mahalaxmi temple of
Patan in India.
3) Followed with time, the Car-vary shifted to softer rock material like soapstone,
steatite (Talc), slates and Marbles. In Gujarat and Rajasthan, carving on red and
white stone and on marble is found in the form of statues.
4) But the sculpture on the hard and massive, largely monolithic stones found its
presence at great extent in the history of sculpture. Stone sculpture is found
generally in hilly, rocky areas mainly in form of the caves.
Perhaps no branch of human culture reflects with greater exactitude the
progress or decadence of man than architecture. The progress of Indian architecture
from the primitive to the sophisticated is example of progressive historical process. In
geologic time and with the progressive growth of human race and culture the earth
material available in surrounding and/or nearby were mainly used for living and
protection. In the development of architecture, from the most primitive types of
human habitation and settlements to magnificent temples and palaces, we can detect
the aesthetic taste which actuated man to combine beauty with utility and his ceaseless
efforts to express his social and religious environment and his attitude towards life.
India is among one of the rare and unique countries in the world which stands
for its ancient cultures and traditions, which range through a span of centuries. It is
clearly evident from the remains of the ancient monuments and traces in the different
parts of India. The Indian monuments are the living examples which take us back to
thousands of years and helps in exploring the history of India. These monuments-
dominated by Megalithic structures - which are in large stone that has been used to
construct a structure or monument, either alone or together with other stones, utilizing
an interlocking system without the use of mortar or cement. The construction of these
structures took place mainly in the Neolithic and continued into the Chalcolithic and
Bronze Age, in India offers a great help to study and know more about the ancient
civilizations of India.
In accordance with the Geology of India, the development of art and
architecture in India has taken place which is reflected in form of magnificent
structures either individually or in collective groups. The continuation (extension),
renovation and newer design adaption in some structures also tells us about the
reviewing attitude of the constructors along with the conservation and protection of
these monuments. However with the passage of time and changing political scenario,
Iconoclasm, passive mind set towards national properties, non-maintenance etc.
sometimes combined with natural hazards, weathering process, climate conditions,
and topography etc. has either destroyed completely or left these monuments as partial
ruins. Whatever is left behind is our pride and national heritage. Protection,
reconstruction or renovation by maintaining the originality of such monuments and
their conservation is a policy of our Indian Government which is implemented through

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Dr Vadagbalkar S.K.
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Archaeological Department. In this context, Geo-archaeological knowledge is
essential. Natural stone, similar to other nature-derived materials, can be highly prone
to deterioration, both due to improper use and or deterioration in the quality of the
environment to which it is exposed. This is followed by loss of its integrity and
function. The knowledge of stone properties, their development through time and
under weathering conditions therefore constitutes a crucial part of natural stone
research.
Although highly durable when properly applied, no stone type can be
considered immortal (Schaffer 1932) and most of the stone varieties are affected by a
polluted atmosphere (Winkler 1997). Deteriorated stone on monuments should be
preferably replaced by stone varieties of the same composition from the same
quarries. However, this is often not possible, and so stone having similar properties
and appearance must be sourced (Prˇikryl 2007). The main aim of this research is to
seek compatible stones in terms of appearance and geochemical-physical properties.
This task requires a thorough understanding of both the rock properties and its
response to external conditions and weathering agents.
Weathering Characteristics:
Climate, which is usually measured in terms of temperature and moisture, can
drastically affect the rate and type of weathering. In an area with cold temperature, for
instance, frost wedging would be the dominant form of physical weathering. Chemical
weathering occurs most rapidly in a high temperature climate. Though Weathering is a
slow process, rock that is exposed to the atmosphere tends to weather much quicker.
Mineral composition is also affected by physical weathering a natural process of
physical disintegration of a rock into smaller fragments, each with the same properties
as the original (without changing the chemical composition), under the effect of
mainly by variations in temperature and pressure. The basic types include Frost action
(in cold climate area), Abrasion (action by running water), Exfoliation- Surface
fracturing (effect of release of pressure), Minerals that are soft (hardness lower than
six) can be easily abraded and worn down.
All chemical and physical properties are determined by the mineral
composition of the rock. Mineral composition is more important in determining the
rate of chemical weathering- process by which the internal structure of a mineral is
altered by the addition or removal of elements. Change in phase (mineral type) and
composition are due to the action of chemical agents. Chemical weathering is
dependent on available surface for reaction temperature and presence of chemically
active fluids. Smaller particle sizes weather by chemical means more rapidly than
large particles due to an increase of surface area. Those minerals that are most reactive
with acids, water, and air are weathered at a more rapid rate e.g. calcite (calcareous-

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Dr Vadagbalkar S.K.
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carbonate matter) in Marbles, limestone, Basalts etc., Feldspars in Granite, Gneiss and
Sandstones.
The general pattern of weathering can be compared with the chart given below, for
any region.



Stone/Rock Properties and Sculpturing:
All stone can be identified by the chemical composition of the mineral (a pure,
solid crystalline substance) or the combination of minerals and non-crystalline
substances of which it is made up. The study of rocks is based on a science that uses
many properties for identification and classification. Understanding these properties
will not only help sculptors understand the materials they are using, but will help them
in the selection and carving of stone. Not all properties are relevant to sculptors; those
that are useful are described in detail here:
Hardness-This describes a stones ability to resist abrasion or scratching, or the
ability of one substance to scratch another. Geologists use the Moh's Hardness Scale
based on 10 minerals as an arbitrary way to test this property:
H-1 Talc, H-2 Gypsum, H-3 Calcite, H-4 Fluorite, H-5 Apatite, H-6 Orthoclase, H-7
Quartz, - (Hardness 1 to 7 is common range of Normal Rock forming Minerals used
for construction)
H-8 Topaz, H- 9 Corundum, H-10 Diamond,- (Hardness 8 to 10 is common range of
minerals used as Gem or Precious/Ornamental stones)
The rocks with minerals that can be scratched by a fingernail (H- 2.5) are called "very
soft", and those that can be scratched by a copper penny (H- 3.5) are called "soft".(
e.g. Marble, Soapstone, Slate) Those that can be scratched by a pocket knife (H- 5.5)
are called "semi-hard"(e.g. Schist, Limestone, Vesicular basalt) and those that cannot
be scratched by a pocketknife(H- 6- 7) "hard"(e.g. Massive Basalt, Sandstone) and
Weathering Regions

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Dr Vadagbalkar S.K.
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those that cannot be scratched by a steel file(H-7) are called "very hard" (e.g. Granite,
Charnockite, Gneiss, Quartzite)
Toughness and Brittleness- These properties are often confused with the
hardness of a mineral. A "fragile" mineral is one that is easily split or broken into
pieces. The term "brittleness" is another term that is applied to a mineral that rather
than pulverize tends to shatter. This could be a soft mineral such as a piece of Talc
(hardness = 1) or it could be a piece of Quartz (hardness = 7). A piece of Jade, on the
other hand although having a hardness less than or equal to a piece of glass may not
break even when hit with a hammer. The term for this is called "toughness".
A stone that is not brittle is often difficult to split when driving a wedge or chisel into
the stone. Rather than allowing the tool to drive into the stone to split it apart, these
stones will tend to pulverize around the tool leaving just small chips and powder. The
quality of brittleness is also important when carving. When carving a brittle stone it
may be easier to crack or shatter the stone if hit too hard. Alternatively a stone that is
not brittle that is hit too hard will crush that section of the stone leaving what is called
a "bruise". Bruises must be eliminated by carving or sanding deeper to remove it, or
will show up on the finished piece. The effect of bruising or leaving tool marks in a
stone is also an effective way to contrast one area of the sculpture with another area
that is highly polished. This technique is often called "texturing" the stone e.g. Fine
grained, compact and massive - Sandstone, Granite, Charnockite, Basalt and Marble.
This is another indicator of how a stone breaks, also described using the term
"layering" or "grain". Those minerals with a strong layering will break in a predictable
manner, called cleavage or weak planes, giving a generally flat plane according to the
crystal structure. Although many stones do not have strong cleavage almost all will
exhibit some of this property on close inspection. The surfaces of those that do not
break in a predictable manner are called fracture. Some brittle stones fracture in with
patterns of curved ripples similar to the pattern and shape of a clam shell. This
phenomenon is called conchoidal fracturing. Cleavages and/or fracture in rocks affect
the shaping-crafting in them. In many monumental sculptures, due to such characters,
non-uniformity, damages and asymmetry is observed, especially where they are hewn
in Schist, weak foliated Gneisses, Shale, vesicular / amygdaloidal Basalts, Limestone,
Quartzite and Marbles.
Density - The density of a stone is typically measured as the mass of a stone
per unit of volume (grams per cubic centimeter), known as the specific gravity. The
specific gravity measures how many more times the stone will weigh compared to an
equal volume of water which weighs 1 gram per cubic cm or one thousand kg per
cubic meter- e.g. a mineral with a specific gravity of 5 will have 5 times the weight of
a similar volume of water. A very light mineral will have a specific gravity that is less
than 2, and a heavy mineral will have a specific gravity greater than 10.

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Dr Vadagbalkar S.K.
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For a sculptor a more commonly used measure of the density is pounds per cubic foot,
of which water weighs about 62.5 pounds. Some examples of common stones are:
Calcite (Marble) SG = 2.71 (170 pounds)
Gypsum (Alabaster) SG = 2.35 (147 pounds)
Colour - Some pure minerals occur mainly in one distinctive color, others may
occur in many different colors. For the purpose of sculpture the purity of stone is not
really a factor but it is attractiveness and further assuming that the impurities do not
affect the ability of the stone to be carved. Because most stones are often a mixture of
minerals, it is possible to find the same types of stone in a never ending variety of
colors and patterns.
A stone that is durable, heavy , attractive coloured, fine grained, compact and
massive which can be cut or finished accurately to definite shape and size; thick-
bedded, evenly grained rock which can be easily cut in any direction and dressed for
masonry; is generally considered as the favourable stone for art and architecture.
Replacement of once deteriorated parts of stone construction raises important issues
concerning the compatibility of fresh versus weathered and or original versus new
(alien) stone varieties. The restoration of monuments also requires solid knowledge on
the past resources that have ceased to be available over the past century.
Indian Geological Setting:
Geology of India is as diverse as its geography and people. It contains rocks
covering almost the entire spectrum of the Geological Time Scale – ranging from
present to past about 3800 million years.
1) The Archeans:- Dharwar and Peninsular Complex - The term Archean refers to
fundamental and very ancient complex unit of rocks like Gneisses, Schists,
Granulites and Granites which constitutes the basement platform on which all
younger sedimentary and volcanic formations rest. As these rocks are crystalline
Igneous and/or re crystalline Metamorphic, are generally hard, compact and
massive in nature. With the geological time and natural wear and tear the Schists
and Gneisses-which have banded or parallel elongated mineral orientations - when
exposed on surface disintegrate and decompose faster than Granites and granulites-
which have fine grained rounded minerals. Marbles and Schists are relatively
softer than other rocks.
In India Archeans are found in abundance and cover nearly 2/3
rd
of the Peninsular
India. i.e. they are very well exposed in larger parts of South-India- Karnataka,
Andhra Pradesh, Tamilnadu and Kerala, Aravallies in Rajasthan, some parts of
Madhya Pradesh, Maharashtra, Goa, Singhbhum and adjoining parts in Bihar,
Orissa and Eastern-Ghats ranges.
Granites, Charnockites and massive Gneiss forms very durable monumental and
ornamental stone. These are compact with homogenous grain nature. Having wide
range in appearance and colour- white, pink, red, grey, black etc., are found used

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Dr Vadagbalkar S.K.
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widely in ancient temples and palaces in South India, which stand today almost
intact after centuries of wear.
The Marbles of crystalline nature with beautiful white colour mainly comes from
Aravalli- Rajasthan – in which famous Taj Mahal is built, along with coloured
varieties from surrounding areas, used as ornamental and decorative stone. Due to
relatively soft nature (hardness 3) combined with fine grained, homogeneity and
massiveness these are widely used. These get fine polish and delicate carvings and
sometimes even transparency. The accessibility of this stone nearby gave stimulus
to Moghul taste for architecture in the seventeenth century. However with the
passage of time on exposure to rains, moisture, snow, micro plants growth on
surface, due to variations in temperature, climate, atmosphere either naturally or
artificially can bring out drastic changes in appearance, and durability (strength) of
rocks.
2) Cuddapah Super group: - The name of this system has been derived from the
Cuddapah basin of Andhra Pradesh where they are well exposed .It mainly
includes marine sediments, which are metamorphosed from lower to medium
grade i.e. meta sediments as Quartzite, Slates, Phyllites intercalated with Shale in
layers and Marbles. Equivalents of Cuddapahs are mainly found in parts of Delhi,
Rajasthan in some parts of Vidarbha and Kolhapur in Maharashtra and Karnataka.
3) Vindhyan Super group: - The Vindhyan constitutes mainly un-metamorphosed
marine sedimentary rock layers of Limestone, Sandstones and Shales. The
Vindhyan rocks are mainly well exposed in parts of Madhya Pradesh and their
equivalents in certain parts of Andhra Pradesh and Karnataka. Massive varieties of
different colored lime stones were mainly used as decorative stones. Lime stones
were mainly used in preparation of lime (by burning) to use as binding material, to
strengthen the structures. Normally in dry climate lime stones are hard stones, but
in acidic environment and heavy rains, they decompose easily.
Bedded and massive varieties of Sandstones have proved their importance in
building of huge structures like forts, palaces, temples, buildings etc. Especially
fine to medium grained and compact varieties have been used for sculpturing.
Coarse grained varieties are found susceptible for weathering and erosion, hence
were not used for delicate works.
4) Gondwana Super group: - The name of this formation is derived from the Gond
– then kingdom in Madhya Pradesh. The Gondwana rocks are mainly fresh water
sediment layers in form of sand, silt and clay mixed with coal beds are found
deposited in shallow, elongated basin brought about by block faulting. The
Gondwana rocks are distributed in parts of West Bengal, Bihar, Madhya Pradesh,
Maharashtra and Orissa states-seen well exposed in Damodar and Son valley,
Upper Narmada and Godavari valley and Mahanadi valley.

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Dr Vadagbalkar S.K.
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5) Deccan Trap: - The Deccan Trap is one of the largest volcanic igneous province
exposures on land in peninsular India, covering nearly 80% of state of Maharashtra
and adjoining parts in Madhya Pradesh, Gujarat, Andhra Pradesh and Karnataka. It
consists of multiple layers of solidified flood basaltic rocks.
The Ajanta caves have been cut into the 200 m-thick Deccan trap basalts. The
thickness of individual flow varies from 1.5 m to 30 m. The various types of traps
recognised in the caves are: 1. Vesicular (a) hard vesicular with or without
amygdales-porphyritic/non-porphyritic. (b) Soft vesicular with or without
amygdales – porphyritic / non-porphyritic. 2. Massive (a) coarse-trap- porphyritic /
non-porphyritic (b) fine trap-porphyritic/non-porphyritic
Though a pick-axe was used initially for the excavation, the finishing and carving
were done mostly by hammer and chisel. The entire works of quarrying of stones,
dressing and finishing were done simultaneously with great care and precision.
From the methods of excavation and support followed it seems likely that the
ancient builders had sufficient knowledge of the principle of single and multiple
beams and cantilever system for distributing the loads.

Examples of Natural damages: (In Maharashtra)
1) A beautiful little island, named Elephanta, located about 11 km off Bombay is
famous not only for its picturesque surrounding but also for its treasure of
sculptures in a rock-cut cave temple was built around the same period or a little
later (850 A.D.) as the Ellora temple. It has the same style of architecture as that of
the Kailasa temple of Ellora, representing the latest phase of rock-cut architectural
activity in India. The Elephanta cave is a Siva shrine. The beautifully carved
columns of the hall and the entrance have square sections at the basal part that
become circular with bas-relief ended with apsidal towards the top. The Elephanta
cave, like Ajanta and Ellora, has been carved out in the Deccan trap basalt, and the
carvings are mostly in soft vesicular type of flow layers. Removal of the zeolite
from the vesicles by the natural processes has given pitted appearance to many of
the carvings. Weathering along the flow junction and joint planes in the rock, are
responsible for damaging parts of the temple walls or columns as well as for the
mutilation of the carvings.
2) Ajanta and Ellora Caves in Maharashtra, India often and has been deeply
influenced by these 2000-year-old caves. In these caves, Hindu and Buddhist
monks have painted and carved on the stone walls for decorative as well as record
purposes. Most of these caves have not been maintained well and the passage of
time is clearly marked on the beautiful art. Ellora Caves Paintings and Sculptures
Damaged by Rainwater. The ancient Ellora caves in Aurangabad city, India were
constructed between the fifth and tenth centuries AD by Hindu, Buddhist and Jain
monks. Now the sculptures and famous paintings in the caves are starting to lose

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Dr Vadagbalkar S.K.
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their gleam, due to rainwater seepage. It is the largest monolithic structure in the
world, carved top-down from a single rock. It contains the largest cantilevered
rock ceiling in the world. The Ellora rock-cut caves, the most spectacular of India's
monuments, are located 29 km northwest of Aurangabad. The majestic beauty, the
architectural style and the sculptures carved out of the Deccan trap rocks of Ellora
have been acclaimed by the entire world. The excavations were executed in
different periods. The contruction was started in 2.5 century A.D. and was
continued later in the 5th and 6th centuries A.D. in the Buddhist style of
architecture. The construction activity,between 6th and 9th century A.D. was
continued, mostly by the Hindus and Jains.
Author: - Dr. Vadagbalkar S.K.
Head and Associate professor in Geology
D.B.F. Dayanand College of Arts and Science, Solapur- Maharashtra State
Email: [email protected]
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Bulletin; 1109, 1–78
Krishnan, M.S.(1982). Geology of India and Burma.(6th Ed.). CBS Publishers;. India, 536p
Pascoe, E.H. (1973). A manual of Geology and Burma, Geological Survey of India, Publication, 485p

PRˇIKRYL,R. (2007). Understanding the earth scientist’s role in the pre-restoration research of
monuments: an over-view;. In : PRˇIKRYL, R. & SMITH, B. J. (eds) Building Stone Decay: From
Diagnosis to Conservation. Geological Society, London, Special Publications, 271, 9–21.

Schaffer, R.J. (1932). The Weathering of Natural Building Stones; Donhead facsimilie, 2004

The Monuments of India, First Online: May 27, 2000.

Wadia, D.N.(1976). Geology of India (4th Ed.);.Tata-McGraw-Hill Publ.co, New Delhi, 254p.

Winkler, E. M. 1997 Stone in Architecture; 3rd ed.; Springer-Verlag , Berlin
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10. Importance of Geology in Rock Monuments
Dr Vadagbalkar S.K.
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Illustrative Figures:







Pitted and rough surface due to vesicles and zeolites (amygdales) in Basalts
1- Ellora caves (Aurangabad) and in 2- Elephanta caves (Mumbai)


Marble? Statue! Highly Weathered Weathering in Sandstone
1
2