In this PPT you will know about the what is the texture of igneous rock and what is the Structure of Igneous Rock and their Types. In this PPT you will know about the what is the texture of igneous rock and what is the Structure of Igneous Rock and their Types. In this PPT you will know about the what is the texture of igneous rock and what is the Structure of Igneous Rock and their Types.

3. • NITYA PARASHAR
• NISHA CHOURASIYA
• PRANAV TIWARI
• PRINCE RAJ SINGH
• SHOBHIT DAHIYA
• VAISHNAVI UPADHYAY

5. IGNEOUS ROCKS ARE FORMED WHEN MOLTEN
ROCK COOLS AND SOLIDIFIES. THEY ARE ONE
OF THE THREE MAIN TYPES OF ROCKS,
ALONG WITH SEDIMENTARY AND
METAMORPHIC ROCKS. IGNEOUS ROCKS CAN
FORM BENEATH THE EARTH'S SURFACE OR AT
ITS SURFACE AS LAVA. THEY ARE DIVIDED
INTO TWO GROUPS, INTRUSIVE OR EXTRUSIVE,
DEPENDING ON WHERE THE MOLTEN ROCK
SOLIDIFIES.
E.G:- OBSIDIAN,BASALT,APLITE,ETC.

6. "TEXTURE" REFERS TO THE
SIZE, SHAPE, AND ARRANGEMENT
OF MINERAL GRAINS OR CRYSTALS
WITHIN A ROCK. IT PROVIDES
INFORMATION ABOUT THE
CONDITIONS UNDER WHICH THE
ROCK FORMED, PARTICULARLY THE
RATE OF COOLING OF THE MOLTEN
MATERIAL THAT LED TO ITS
SOLIDIFICATION.

7. DEGREE OF CRYSTALLIZATION OR
“CRYSTALLINITY”
SIZE OF THE GRAIN OR “GRANULARITY”
FABRIC

8. WHENTHEMOLECULESINAROCKHAVESETTLED
DOWNINTOASTABLEARRANGEMENTANDWITHA
RECOGNIZABLEPATTERNISCALLEDCRYSTAL..
ITISADEFORMEDSTATEOFCRYSTALLIZATION,
REGARDEDASANAMORPHOUSSOLID.INAGLASS,THE
MOLECULESHAVESETTLEDDOWNINTOASTABLE
ARRANGEMENTWITHOUTANYRECOGNIZABLEPATTERN

9.  RATE OF COOLING OF MAGMA
VISCOSITY OF MAGMA
 RAPID COOLING AND HIGH
VISCOSITY FAVOR THE FORMATION
OF GLASS.
 SLOW COOLING AND LOW VISCOSITY
PROMOTES THE FORMATION OF
CRYSTAL.

10. CRYSTALLINITY REFERS TO THE
DEGREE OF CRYSTALLINE
STRUCTURE PRESENT IN THE ROCK.
TYPES OF CRYSTALLINITY
 HOLOCRYSTALLINE
 HEMICRYSTALLINE / MEROCRYSTALLINE
 HOLOHYALINE

11. A HOLOCRYSTALLINE ROCK IS
COMPOSED ENTIRELY OF MINERALS
THAT HAVE FORMED RECOGNIZABLE
CRYSTALS DURING THE ROCK'S
COOLING AND SOLIDIFICATION
PROCESS.
E.G:- GRANITE, GABBRO,
SYENITE.

12. WHEN THE ROCK IS
COMPOSED PARTLY OF
CRYSTALS AND PARTLY OF
GLASS THE TERM MERO/
HYPO/ HEMICRYSTALLINE IS
USED.
E.G. RHYOLITE, TRACAYTE.

13. THE ROCK WHICH IS
ENTIRELY COMPOSED OF
GLASSY MATERIALS OR
GLASS IS KNOWN AS
HOLOHYALINE
E.G. OBSIDIAN,
PITCHSTONE.

14. GRANULARITY DEALS WITH THE SIZE OF
THE CRYSTALS IN IGNEOUS ROCKS FROM
ALMOST SUBMICROSCOPIC DIMENSIONS
TO CRYSTAL MEASURABLE IN YARDS.
TYPES OF GRANULARITY:-
a) PHANERIC OR PHANEROCRYSTALLINE
b) APHANATIC

15. If the crystals are visible to
the naked eye or by
ordinary hand lens, the
rock is said to be Phaneric
or Phanerocrystalline.
Phaneric or Phanerocrystalline is
further classified by.
Coarse Grain: > 5 mm
Medium Grain: 5 mm to 1 mm..
Fine Grain: <1 mm fine grain
Medium grain
Coarsegrain

16. If the crystals are not visible to the naked eye or
by ordinary hand lens, the rock is known to be
Aphanitic.
I. Microcrystalline: individual
crystals are distinguishable with the
help of petrographic microscope
.II. Cryptocrystalline: individual
crystals are not distinguishable with
the help of petrographic microscope.
It is classified by:-

17. The fabric or pattern of the rocks depend
on the shapes, relative size and
arrangement of the crystals.
a. Shape of the crystal
b. Mutual relationship of
crystal

18. SUBHEDRAL:
•DEFINITION: SUBHEDRAL CRYSTALS EXHIBIT
SOME, BUT NOT ALL, WELL-FORMED CRYSTAL
FACES. THEY ARE INTERMEDIATE BETWEEN
EUHEDRAL AND ANHEDRAL.
Crystals forms are described with references
of the development of their faces.
. Euhedral:
•Definition: Euhedral crystals are
well-formed crystals that display
sharp, distinct crystal faces
Anhedral:
•Definition: Anhedral crystals are
crystals that lack well-defined crystal
faces. They form within a confined
space or where other minerals or
physical constraints prevent the

19. fabric of a rock is influenced not
only by the shape of the crystals,
but their relative size and their
mutual arrangement.

20. In Equigranular rocks, there is a
relatively uniform distribution of
mineral grains, and they exhibit
similar sizes throughout the rock
mass.
Panidiomorphic : Most of the
crystals are euhedral
Hypidiomorphic : Most of the
crystals are Subhedral
Allodiomorphic : Most of the
crystals are anhedral
panidiomorphic
hypidiomorphic
allodiomorphic

21. Porphyritic texture is a type of
igneous rock texture that occurs in coarse, medium, and
fine-grained rocks. It is defined by the presence of larger
crystals, known as phenocrysts, surrounded by a matrix of
considerably smaller crystals or igneous glass, called
groundmass.
phenocryst
groun
dmass
Porphyritic
texture

22. Porphyritic texture

23. Poikilitic texture refers to igneous rocks where
large later-formed less perfect crystals
('oikocrysts') surround smaller early-formed
idiomorphic crystals ('chadacryst’s') of other
minerals. A poikilitic texture is most easily
observed in petrographic thin sections.

24. Ophitic texture is a variation of the poikilitic texture
where random plagioclase laths are enclosed by
pyroxene or olivine. It is an important variety of basalt
texture where pyroxene forms larger crystals and
typically contains numerous crystals of plagioclase.
OPHITIC TEXTURE

25. When two minerals crystallize simultaneous, they
may result intergrowth texture.
 Graphic intergrowth: intergrowth
between orthoclase (Feldsper) and
Quartz
 Myrmekite intergrowth:
intergrowth between Plagioclase
and Quartz.
 Perthitic
intergrowth:
intergrowth between
Orthoclase and
Albite.

26. Since magma is a fluid, it can flow. If elongate
crystals, such as feldspar are present in the
magma whilst it is flowing, these crystals may
well align themselves in the direction of flow
Directive texture

27. When triangular or polygonal interspaces between the crystals
are entirely filled with granules of other minerals, the texture is
said to be Intergranular. Generally, Basalt shows this type of
texture and the filled granules are olivine, augite.
basalt

31. When lavas heavily charged with gases and other volatiles are erupted on the surface,
the gaseous constituent's escapes from the magma as there is a decrease in the
pressure.
Near the top of the flows in the material, empty cavities, bubbles, vesicles are formed,
which may elliptical, spherical, cylindrical or irregular in shape.
The individual openings are known as vesicles and the structure as a whole is known
as vesicular structure .
If however, the vesicles thus formed are subsequently filled in with some low-
temperature secondary minerals, such as calcite, zeolite, chalcedony etc., these
infillings are called "amygdales".
Amygdaloidal

32.  Since lavas of acidic composition, due
to their high viscosity, do not flow to
greater distances, after solidification
they are found to offer a very rough
surface. Such lava flows are known as
block lava. It is also known as 'aa'
structure.
 Lavas of basic composition are quite
mobile because of their low viscosity
and they can flow to greater distances
and after solidification offers very
smooth surface. Such lava flows are
known as ropy lava and are also

33.  A distinctive form of lava flow in which the solidified
rock forms rounded masses with a glassy exterior.
Pillow lava is found where lava flows into the ocean or a
lake and quickly cools.
The liquid lava forms a sphere when it enters the cold
water as a result of surface tension. These hot balls of
quickly solidifying lava settle to the ground quickly.
 As they settle, they flatten and become pillow like in
form. As more and more pillows settle to the seafloor,
the weight flattens them even more.
Pillow lavas therefore form piles around the vent or
entry point of a lava flow. They make up much of the

34.  Joints are divisional planes which are
found in all kinds of igneous rock
impressed upon them mainly by force
acting from outside. Joints plains may
be vertical or horizontal.
 The horizontal joints planes are
sometimes so closely spaced as to
produce a sheet structure. The sheets
are commonly thinner as the surface
of the ground is approached and
they usually show some degree of
parallelism.

35. Columnar structure refers to the structure of
a mineral aggregate made up of nearly
parallel slender columns that is
intermediate between an equant and
acicular structure. It is found in some
amphiboles.

36. Pegmatites are extreme igneous rock that
form during the final stage of a magma's
crystallization. They are extreme because
they contain exceptionally large crystals
and they sometimes contain minerals that
are rarely found in other types of rocks.
To be called a "pegmatite," a rock should
be composed almost entirely of crystals
that are at least one centimetre in
diameter. Granite and Syenite more often
show this type of structure.

37. Spherulites are typically two-mineral aggregates
(mainly quartz and feldspar), formed by initial
Spherulitic growth of one mineral and later
crystallization of a second mineral from the liquid
or glass between the fibres.
 Spherulitic aggregate
(Spherulites)
 arrays of fibrous
(needle-like, acicula)
 Are common in glassy
felsic volcanic rock

38. Orbicular granite (also known as
orbicular rock or orbiculite) is an
uncommon plutonic rock type which is
usually granitic in composition.
These rocks have a unique appearance
due to orbicules concentrically layered,
spheroidal structures, probably formed
through nucleation around a grain in a
cooling magma chamber