8. Kinds of Igneous Rocks
Extrusive (volcanic)
- forms when magma erupts &
solidifies on the surface
Intrusive (plutonic)
- forms when magma solidifies
within the crust
9.
10.
11. 1. GRANITE
Description: a light-colored igneous rock with grains large
enough to be visible with the unaided eye. It forms from
the slow crystallization of magma below Earth’s
surface.
Characteristics:
• it is hard, tough
• crystalline rock
• very resistant to erosion
Kind: intrusive igneous rock
The main processes that affect it are freeze-thaw and
hydrolysis.
12. 2. SYENITE
Description: a coarse-grained igneous rock with a general
composition similar to that of granite, but deficient in
quartz.
Characteristics:
• typically light coloured
• medium to coarse grained
Kind: intrusive igneous rock
Uses: dimension stone for building facings, can be used
as aggregates in t5he building and roading industry
13. 3. DIORITE
Description: a speckled, coarse-grained
igneous rock consisting essentially of
plagioclase, feldspar, hornblende or other
mafic minerals.
Characteristics:
• color is medium gray and green
• coarse grained texture
Uses: used as construction material of
roads, buildings and also drainage stone
for erosion control
Kind: intrusive igneous rock
14. 4. GABBRO
Description: is a coarse-grained composed mainly of
plagioclase and augite. It is the most abundant
rock in the deep oceanic crust.
Characteristics:
• dark-colored
• black or dark grey
• medium to coarse grained
Kind: intrusive igneous rock
Uses: used as aggregate in construction
and roading industry, building facings,
foyers
15. 5. PEGMATITE
Description: an igneous rock composed almost
entirely of crystals that are over one centimetre in
diameter.
Characteristics:
• large crystals
• rare minerals
• pink, grey-white
Kind: intrusive igneous rock
Pegmatites are formed as part of the cooling and
crystallization process of intrusive rocks.
16. 6. DIABASE ( DOLERITE )
Description: a dark-colored igneous rock which is a
common rock type. It is compositionally equivalent to
gabbro and basalt.
Characteristics:
• dark-colored
• common rock type
Kind: intrusive igneous rock
Dolerite cools under basaltic volcanoes. It cools
moderately quickly when magma moves up into
fractures and weak zones below a volcano.
17. 7. BASALT
Description: a fine-grained composed mainly of
plagioclase and pyroxene
Characteristics:
• dark-colored
• fine-grained
• abundant on moon
• often have holes
Kind: extrusive igneous rock
Uses: most commonly crushed for use as an
aggregate in construction projects, road base, railroad
ballast.
24. 1. SANDSTONE
Description: is a sedimentary rock composed of sand-size
grains of mineral, rock, or organic material.
Characteristics:
• consist of mineral particles
• very porous
• brown, red, purple, and pink
Group: clastic sedimentary rock
25. 2. LIMESTONE
Description: made of calcium carbonate by the mineral
calcite. It is formed by the accumulation of coral, shells,
and other marine debris.
Characteristics:
• grey/yellow
• rough but soft
• easily breakable
• gives off gas bubbles
• permeable
• can be weathered easily
Group: organic sedimentary
rock
26. 3. SHALE
Description: sedimentary rock that composed o
predominance of silt and clay other minerals, especially
quartz and calcite.
Characteristics:
• black/grey
• very fine grained
• contains clay particles
Group: clastic sedimentary rock
27. 4. CONGLOMERATE
Description: a sedimentary rock that forms from the
cementing of rounded cobble and pebble sized
fragments.
Characteristics:
• rounded clasts
• unique clast composition
• uniform clast-size
Group: clastic sedimentary rock
28. 5. BRECCIA
Description: a sedimentary rock that formed from
angular gravel and boulder size clasts cemented
together in a matrix.
Characteristics:
• colorful rock
• angular gravel
Group: clastic sedimentary rock
29.
30.
31. 1. QUARTZITE
Description: a metamorphic rock formed under
moderate to high grade metamorphism that
exhibits both foliated and non foliated structure.
Characteristics:
• looks like sandstone
• much harder, sand cannot be rubbed off
• may show choncoidal fracture
Formation: heat and pressure on sandstone that is
cemented with silica lead t5o crystallization of the
silica cement and sand particles.
32. 2. MARBLE
Description: a metamorphic rock formed when
limestone is subjected to high pressure or heat.
Characteristics:
• white stone
• sugary appearance
The foliation in slate is called “slaty cleavage”
33. 3. SLATE
Description: a fine grained, foliated, homogeneous
metamorphic rock derived from an original shale
type sedimentary rock composed of clay or
volcanic ash.
Characteristics:
• fine-grained
• bluish black
• fine texture
Composition: tink when struck
34. 4. GNEISS
Description: a medium to coarse grained
metamorphic rock. It is characterized by
alternating light and dark bands differing in
mineral composition.
The lighter bands contain mostly
quartz and feldspar, the darker often
contains biotite, hornblende, and
graphite.
35. 5. SCHIST
Description: an intermediate to high grade, foliated
metamorphic rock.
Characteristics:
• highly variable in appearance
• medium to large sized crystal
• platy minerals predominate
