This document provides information about the classification and characteristics of limestone and sandstone. It begins by defining limestone as a sedimentary rock composed mainly of calcium carbonate in the form of calcite and aragonite. It describes the microscopic components of limestone including skeletal fragments, ooids, peloids, and lime mud. It explains that limestone forms most readily in warm, shallow marine environments. The document then discusses various types of limestone based on composition and texture. It concludes by outlining some of the major uses of limestone, particularly in construction as a crushed stone for concrete, cement production, and road base. The document also provides definitions of quartz arenites, feldspathic arenites, and lith

1. ID:160080009
SUNKARA DEVIPRASANTH
PETROLEUM ENGINEERING
WITH THE REFARANCE OF :Principles of
Sedimentology and Stratigraphy

2. Classification of limestone and sandstone
Sandstone.
Sandstones make up 20-25 percent of all
sedimentary rocks. They are common rocks in
geologic systems of all ages, and they are
distributed throughout the continents of Earth.
Sandstones consist mainly of silicate grains
ranging in size from 1/16 to 2 mm. These particles
make up the framework fraction of the sandstones.
Sandstones may also contain various amounts of
cement and very fine size ( < -0.03 mm) material
called matrix, which are present within interstitial
pore space among the framework grains. Because
of their coarse size ,the framework milleralogy of
sandstones can generally be determined with
reasonable accuracy with a standard petrographic
microscope or by backscattered electron
microscopy .Bulk chemical composition can be
measured by instrumental techniques such as X-

3. ray fluorescence and inductively coupled argon
plasma emission spectrometry . The chemistry of
individual mineral grains is commonly determined
by use of an electron probe microanalyzer or an
energy dispersive X-ray detector attached to a
scanning electron microscope. In this section, we
discuss the classification of sandstones on the
basis of mineral composition, and evaluate the
usefulness of particle and chemical composition in
interpreting the genesis of sandstones.
Descriptive classification of sandstones is based
fundamentally on framework mineralogy, although
the relative abundance of matrix plays a role in
some classifications. Although mineralogy is the
principal basis for classifying sandstones, finding a
classification that is suitable for all types of
sandstones and acceptable to most geologists has
proven to be an elusive goaL In fact, more than
fifty different classifications for sandstones have
been proposed (Friedman and Sanders, 1978), but
none has received widespread acceptance.
Classifications that are all-inclusive tend to be too
complicated and unwieldy for general use Most
sandstones are made up of mixtures of a very
small number of dominant framework components.
Quartz, feldspars, and rock fragments such as
chert and volcanic clasts are the only framework
constituents that are commonly abundant enough
to be important in sandstone classification. In

4. addition to framework grains, matrix may be
present in interstitial spaces among these grains.
In spite of the very simple composition of
sandstones, geologists have not been able to
agree on a single, acceptable sandstone
classification. Published classifications range from
those that have a strong genetic orientation to
those based strictly on observable, descriptive
properties of sandstones. sandstones that are
effectively free of matrix ( <5 percent) are
classified as quartz arenites, feldspathic arenites,
or lithic arenites depending upon the relative
abundance of QFL constituents. If matrix can be
recognized (at least 5 percent), the terms quartz
wacke, feldspathic wacke, and lithic wacke are
used instead .
General Characteristics of Major Classes of
Sandstones The preceding discussion indicates
that sandstones can be divided on the basis of
framework mineralogy into three major groups:
quartz arenites, feldspathic arenites, and lithic
arenites
Quartz Arenites Quartz arenites are composed of
more than 90 percent siliceous grains that may
include quartz, chert, and quartzose rock
fragments .They are commonly white or light gray
but may be stained red, pink, yellow, or brown by
iron oxides. They are generally well lithified and
well cemented with silica or carbonate cement;

5. however, some are porous and friable. Quartz
arenites typically occur in association with
assemblages of rocks deposited in stable cratonic
environments such as eolian, beach, and shelf
environments. Thus, they tend to be interbedded
with shallow-water carbonates and, in some
cases, with feldspathic sandstones. Most quartz
arenites are texturally mature to supermature ,
quartz wackes are uncommon. Cross-bedding is
particularly characteristic of these sandstones, and
ripple marks are moderately common. Fossils are
rarely abundant, possibly owing to poor
preservation or to the eolian origin of some quartz
arenites, but fossils may be present. Also, trace
fossils such as burrows of the Skolithos facies may
be locally abundant in some shallow-marine quartz
arenites. Quartz arenites are common in the
geologic record. Pettijohn estimates that they
make up about one-third of all sandstones. Quartz
arenites can originate as first-cycle deposits
derived from primary crystalline or metamorphic
rocks.
Feldspathic Arenites Feldspathic arenites contain
less than 90 percent quartz, more feldspar than
unstable rock fragments, and minor amounts of
other minerals such as micas and heavy minerals.
Some feldspathic arenites are colored pink or red
because of the presence of potassium feldspars or
iron oxides; others are light gray to white. They are

6. typically medium to coarse grained and may
contain high percentages of subangular to angular
grains. Matrix content may range from trace
amounts to more than 15 percent, and sorting of
framework grains can range from moderately well
sorted to poorly sorted. Thus, feldspathic
sandstones are commonly texturally immature or
submature. Feldspathic arenites are not
characterized by any particular kinds of
sedimentary structures. Bedding may range from
essentially structureless to parallel laminated or
cross laminated. Fossils may be present,
especially in marine beds. Feldspathic arenites
typically occur in cratonic or stable shelf settings,
where they may be associatedwith
conglomerates, shallow-water quartz arenites or
lithic arenites, carbonate rocks, or evaporites. Less
typically, they occur in sedimentary successions
that were deposited in unstable basins or other
deeper water, mobilebelt settings. Feldspathic
arenites of the latter types, which are commonly
matrix rich and well indurated owing to deep burial,
are often called feldspathic graywackes. The
abundance of feldspathic arenites in the geologic
record is not well established. Pettijohn (1963)
estimates that arkoses make up about 15 percent
of all sandstones. If feldspathic graywackes are
included, feldspathic arenites are probably more
abundant than 15 percent. Some arkoses originate
essentially in situ when granite and related rocks

7. disintegrate to produce a granular sediment called
grus. These residual arkosic materials may be
shifted a short distance downslope and deposited
as fans or aprons of waste material, commonly
referred to as clastic wedges. These fans may
extend into basins and become intercalated or
interbedded with better stratified and better sorted
sediments. Other feldspathic arenites undergo
considerable transport and reworking by rivers or
the sea before they are deposited. These
reworked sandstones commonly contain less
feldspar than do residual arkoses, and they are
better sorted and grains are better rounded. Most
feldspathic sandstones are derived from granitic-
type primary crystalline rocks, such as coarse
granite or metasomatic rocks containing abundant
potassium feldspar. Feldspathic arenites
containing feldspars that are dominantly
plagioclase, derived from igneous rocks such as
quartz diorites or from volcanic rocks, are also
known. The preservation of large quantities of
feldspars during weathering appears to require
that feldspathic arenites originate either in very
cold or very arid climates, where chemical
weathering processes are inhibited, in warmer,
more humid climates where marked relief of local
uplifts allows rapid erosion of feldspars before they
can be decomposed. Although some feldspars
may survive recycling from a sedimentary source,
it appears unlikely that sedimentary source rocks

8. can furnish enough feldspar to produce a
feldspathic arenite or arkose. Feldspathic arenites
occur in sedimentary successions of all ages,
although they appear to be particularly abundant in
Mesozoic and Paleozoic strata. Some common
examples include the Old Red Sandstone in
Scotland, the Triassic Newark Group in the New
Jersey area, the Pennsylvanian Fountain and
Lyons formations of the Colorado Front Range,
and the Paleocene Swauk Formation of
Washington. The Swauk Formation is particularly
interesting because it is a plagioclase arkose.
Lithic Arenites Lithic arenites are an extremely
diverse group of rocks that are characterized by
generally high content of unstable rock fragments
such as volcanic and metamorphic
CONGLOMERATES
The term 'Conglomerates is used in this book as a
general class name for sedimentary rocks that
contain a substantial fraction (at least 30 percent)
of gravel-size (>2 mm) particles which are
composed of very angular, gravel-size fragments,
are not distinguished from conglomerates in the
succeeding discussion. Conglomerates are
common in stratigraphic successions of all ages
but probably make up less than l percent by weight

9. of the total sedimentary rock mass . They are
closely related to sandstones in terms of origin and
depositional mechanisms, and they contain some
of the same kinds of sedimentary
Particle Composition Conglomerates. may contain
gravel-size pieces of individual minerals such as
quartz; however, most of the gravel-size
framework grains are rock fragments (clasts).
Individual sand- or mud-size mineral grains are
commonly present as Clast-supported
conglomerate underlying laminated sands. Any
kind of igneous, metamorphic, or sedimentary rock
may be present in a conglomerate, depending
upon source rocks and depositional conditions.
Some conglomerates are composed of only the
most stable and durable kinds of clasts (quartzite,
chert, vein-quartz). Stable conglomerates
composed mainly of a single clast type are
referred to by Pettijohn (1975) as oligomict
conglomerates. Most oligomict conglomerates
were probably derived from mixed parent-rock
sources that included less stable rock types.
Continued recycling of mixed ultrastable and
unstable clasts through several generations of
conglomerates ultimately led to selective
destruction of the less stable clasts and
concentration of stable clasts. Conglomerates that
contain an assortment of many kinds of clasts are
polymict conglomerates. Polymict conglomerates

10. that are made up of a mixture of largely unstable
or metastable clasts such as basalt, limestone,
shale, and metamorphic phyllite are commonly
called petromict conglomerates (Pettijohn, 1975).
Almost any combination of these clast types is
possible in a petromict conglomerate. The matrix
of conglomerates commonly consists of various
kinds of clay minerals and fine micas and/ or silt-
or sand-size quartz, feldspars, rock fragments, and
heavy minerals. The matrix may be cemented with
quartz, calcite, hematite, clay, or other cements.
Classification Conglomerates can originate by
several processes, We are interested most in
epiclastic conglomerates, which form by
breakdown of older rocks through the processes of
weathering and erosion. Epiclastic conglomerates
that are so rich in gravel-size framework grains
that the gravel-size grains touch lfundamental
types
Major types -Epiclastic conglomerate and breccia
,Volcanic breccia ,Cataclastic breccia ,Solution
breccia,Meteorite impact breccia .
Limestone is a sedimentary rock, composed mainly of
skeletal fragments of marine organisms such as coral,
forams and molluscs. Its major materials are the
minerals calcite and aragonite, which are different
crystal forms of calcium carbonate (CaCO3).calcite is

11. one the mineral and its crystal system is rhombohedral
and aragonite crystal system is orthorhombic.Most
limestones are simply the cemented remains of marine
shells.lime stone anatmy is grains
skeletal particals,ooids

12. ,peloids

13. and lime mud

14. Microscopic crystals produced by calcareous algae and
through abrasion of larger particles and cement

15. Inorganically precipitated CaCO3 crystals and where do
the limestone from Because CaCO3 precipitates most
readily in warm, well lit, agitated water of normal
marine salinity…..mostlimestones form in shallow,
tropical depositionalenvironment
e.g Bahamas, central America, Persian Gulf, NW
shelf of Australia, Great Barrier Reef, Malaysia,
Indonesia, whole rock *Crushed limestone
* Dolomitic limestone
Burned lime (calcium oxide) *High calcium lime
*Dolomitic lime

16. Hydrated lime (calcium hydroxide) manufactured
of limestone; quicklime and slaked lime are all
used to neutralise excess acidity - which may
be caused by acid rain - in lakes and in
soils. Limestone is used as a building
material, and to purify iron in blast furnaces.
It's also used in the manufacture of glass, and
of cement (one of the components of
concrete). The texture of the limestone is a
sedimentary rock composed mainly of calcium
carbonate (CaCO3), usually calcite,
sometimes aragonite. It may also contain
considerable amounts of magnesium
carbonate (dolomite, (CaMg)(CO3)2).
Most limestones have a granulartexture,
but limestone can also be massive, crystalline
or clastic.
Varieties of Limestone here are many different
names used for limestone. These names are
based upon how the rock formed, its appearance
or its composition, and other factors. Here are
some of the more commonly used varieties.
Chalk: A soft limestone with a very fine texture
that is usually white or light gray in color. It is
formed mainly from the calcareous shell remains
of microscopic marine organisms such as

17. foraminifers, or the calcareous remains from
numerous types of marine algae.
Coquina: A poorly-cemented limestone that is
composed mainly of broken shell debris. It often
forms on beaches where wave action segregates
shell fragments of similar size.
Fossiliferous Limestone: A limestone that
contains obvious and abundant fossils. These are
normally shell and skeletal fossils of the organisms
that produced the limestone.
Lithographic Limestone: A dense limestone with
a very fine and very uniform grain size that occurs
in thin beds which separate easily to form a very
smooth surface. In the late 1700s, a printing
process (lithography) was developed to reproduce
images by drawing them on the stone with an oil-
based ink and then using that stone to press
multiple copies of the image.
Oolitic Limestone: A limestone composed mainly
of calcium carbonate "oolites," small spheres
formed by the concentric precipitationof calcium
carbonate on a sand grain or shell fragment.
Travertine: A limestone that forms by evaporative
precipitation, often in a cave, to produce
formations such as stalactites, stalagmites, and

18. flowstone.
Tufa: A limestone produced by precipitation of
calcium-laden waters at a hot spring, lake shore,
or other location
Uses of Limestone is a rock with an
enormous diversity of uses. It could be the one
rock that is used in more ways than any other.
Most limestone is made into crushed stone and
used as a construction material. It is used as a
crushed stone for road base and railroad ballast. It
is used as an aggregate in concrete. It is fired in a
kiln with crushed shale to make cement.Some
varieties of limestone perform well in these uses
because they are strong, dense rocks with few
pore spaces. These properties enable them to
stand up well to abrasion and freeze-thaw.
Although limestone does not perform as well in
these uses as some of the harder silicate rocks, it
is much easier to mine and does not exert the
same level of wear on mining equipment,
crushers, screens, and the beds of the vehicles
that transport it.