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Rock Identification Guide
Complete with
photos and information about each rock’s
distinguishing characteristics, this rock
identification guide has been designed to assist
you in identifying the rocks provided in the
Deeper and Deeper and Mining Matters II
kits. This guide also includes information about
how each rock was formed, the location from
where they were collected and their uses in
everyday life.
Year after year
in-kind contributors from the mineral and
aggregate industries provide valuable resources
for our educational units. The sheer number and
variety of rock and mineral samples required for
the production of the units is immense. More
than 60 samples representing 25 different types
of metallic and industrial minerals, aggregates
and the three main rock groups – igneous,
sedimentary and metamorphic – are required for
each kit. The organization relies greatly on
their industry partners, resident geologists
from the Ontario Ministry of Northern
Development and Mines and a crew of students to
aid in the collection and sizing of samples. We
would like to take this opportunity to thank the
many in-kind contributors for their on-going
support.
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Basalt
Rock Type: igneous
(extrusive/volcanic)
Composition: feldspar, olivine,
pyroxene, amphibole
Equivalent to: Gabbro
(intrusive/plutonic)
Environment: Basalt is solidified
lava, like rhyolite. However, it flows
much quicker because it is less viscous.
The Hawaiian Islands are made of
basaltic lava. The ocean floor is also
mostly basalt.
Distinguishing Characteristics:
red-brown to black, frothy with small
visible holes where gas escaped while
the lava cooled.
Origin of your Samples: Sault
Ste. Marie, Ontario
Uses: Basalt is crushed and used
as crushed stone, concrete aggregate and
railroad ballast. Basalt fibres are used
in the production of high quality
textile fibres, floor tiles, basalt
plastic reinforcement bars, basalt fibre
roofing felt and glass wool (fibre
glass).
Basalt samples courtesy
of the Resident Geologist Program,
Ontario Ministry of Northern Development
and Mines. |
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Conglomerate
Rock Type: sedimentary
Composition: fragments of other
rocks and minerals cemented by silica,
calcite, or iron oxide.
Environment: The rock fragments
can be rounded from being rolled along a
stream bed or a beach during
transportation. If the fragments
embedded in the matrix are angular
instead of rounded, the rock is called a
breccia (pronounced BRECH-i-a).
Distinguishing Characteristics:
dark grey with imbedded fragments
Origin of your Samples: Kirkland
Lake, Ontario
Uses: conglomerate is used in the
construction industry
Conglomerate samples
courtesy of the Resident Geologist
Program, Ontario Ministry of Northern
Development and Mines. |
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Dolostone
Rock Type: sedimentary
Composition: dolomite and fossils
Metamorphoses to: marble
Environment: Sea water, high in
magnesium, flows through porous
limestone and replaces some of the
calcium with magnesium turning limestone
into dolostone. Fossils are plants or
animals that have been preserved in rock
as organic carbon, chitin, or some
mineral that replaced the original
tissue. When an animal or plant dies its
body can end up being buried by mud or
other sediments. The hard parts
(skeleton, teeth, shell) and sometimes
tissue (leaves, flowers, muscle,
cartilage) may be preserved when the
sediments become rock.
Distinguishing Characteristics:
Grey with fossils that are visible.
Anything that looks like it was once
alive may be a fossil. Fossils are often
the same colour as the rocks in which
they are found.
Origin of your Samples: Niagara
Escarpment in Milton, Ontario
Uses: Dolostone from the Niagara
Escarpment is used as high quality
construction aggregates. It is found in
asphalt mixes for roads and streets,
high strength concrete mixes used for
high-rise residential buildings, bridge
overpasses, sidewalks and airport
runways. Crushed dolostone is used to
create drainage layers under high volume
roads and is found in uncontaminated
construction fill.
Dolostone samples
courtesy of Dufferin Aggregates, Milton
Quarry. |
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Gabbro
Rock Type: igneous
(intrusive/plutonic)
Composition: feldspar, olivine,
pyroxene, amphibole
Equivalent to: Basalt
(extrusive/volcanic)
Environment: Gabbro is formed by
magma that cools very slowly into hard
rock below or within the Earth’s crust.
Distinguishing Characteristics:
dark grey-black, shiny surfaces of
feldspar are visible.
Origin of your Samples: Tweed,
Ontario
Uses: Gabbro is too fragile to
use in construction. Often chromium,
nickel and platinum occur in association
with Gabbro.
Gabbro samples courtesy
of the Resident Geologist Program,
Ontario Ministry of Northern Development
and Mines. |
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Gneiss
Rock Type: metamorphic
Composition: quartz, feldspar,
mica
Original Rock: granite, gabbro
Environment: Gneiss forms at high
temperatures and pressures. The
temperature needed is about 700°C and
the pressure needs to be about 12-15
kilo bars, which is at a depth of about
40 km!
Distinguishing Characteristics:
banded with alternating layers of dark
and light minerals.
Origin of your Samples: Parry
Sound, Ontario
Uses: Gneiss is used in
construction, aggregate and for
ornamental purposes.
Gneiss samples courtesy
of Fowler Construction Company Ltd. |
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Granite
Rock Type: igneous
(intrusive/plutonic)
Composition: feldspar, quartz,
mica, hornblend
Equivalent to: rhyolite
(extrusive/volcanic)
Environment: Granite is formed by
magma that cools very slowly into hard
rock below or within the Earth’s crust.
Distinguishing Characteristics:
Visible crystals of pink feldspar, white
or grey quartz, and black mica. There is
no horizontal banding in granite.
Origin of your Samples: Belmont
Township, Ontario
Uses: Granite is used for kitchen
countertops and as a decorative building
material. Granite is not fire-safe
because it can crack in high heat.
Granite samples
courtesy of the Resident Geologist
Program, Ontario Ministry of Northern
Development and Mines. |
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Limestone
Rock Type: sedimentary
Composition: mostly calcite
Environment: There are several
ways for limestone to form. Calcite
dissolves easily in warm water but when
the concentration reaches a certain
threshold, the calcite comes out of
solution and is deposited on the sea
floor as a chemical precipitate. The
precipitates can build up along with
other sediments or on their own and
eventually form limestone. Another way
for limestone to form is by the build up
of the shells and skeletons of marine
animals.
Distinguishing Characteristics:
whitish-grey with a chalky texture.
There are no visible fossils in these
samples.
Origin of your Samples: Ingersoll,
Ontario
Uses: This highly pure limestone
is used as flux in the steel making
process and is used in the production of
glass. Other applications include paper
production, sugar refining, acid lake
treatment and flue gas desulphurisation.
Limestone has construction, agricultural
and automotive applications. It is also
supplied to feed mills and chicken
farmers.
Limestone samples
courtesy of Beachville Lime Ltd. |
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Marble
Rock Type: metamorphic
Composition: very pure,
recrystallized calcite
Original Rock: limestone or
dolostone
Environment: Marble forms at many
temperatures and pressures.
Distinguishing Characteristics:
medium to coarser grained, light
coloured and calcite crystals may be
visible. Holing these samples up to the
light and slowly turning them will
reveal a slight sparkle.
Origin of your Samples: Madoc,
Ontario
Uses: Marble is used for
construction, countertops, and carvings,
and may be a source for magnesium.
Marble samples courtesy
of the Resident Geologist Program,
Ontario Ministry of Northern Development
and Mines. |
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Quartzite
Rock Type: metamorphic
Composition: recrystallized
quartz grains
Original Rock: sandstone
Environment: Quartzite forms at
many temperatures and pressures.
Distinguishing Characteristics:
light grey or white, medium grained,
very hard.
Origin of your Samples: Badgeley
Island, Ontario
Uses: Quartzite is the raw
material for the glass and ceramics
industries.
Quartzite samples
courtesy of Unimin Canada Ltd. |
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Rhyolite
Rock Type: igneous
(extrusive/volcanic)
Composition: feldspar, quartz,
mica, hornblend
Equivalent to: granite
(intrusive/plutonic)
Environment: Rhyolite is formed
by magma that has reached the Earth’s
surface (lava) and therefore cools very
quickly. Lava can explode out of a
volcano and make pumice or ash, or flow
down its side and make thick layers of
fine grained rock or volcanic glass.
Distinguishing Characteristics:
Very fine grained, pinkish-grey,
sometimes with dark streaks. If dipped
in water and rubbed on a piece of paper,
rhyolite will likely tear the paper
rather than leave a muddy streak.
Origin of your Samples: Timmins,
Ontario
Uses: Black volcanic glass called
obsidian and frothy-looking white
coloured rock called pumice are other
forms of rhyolite. Pumice is used in
abrasives, concrete, stone-washing
laundries, hand soap, emery boards, and
sandpaper and is used in sandblasting.
Rhyolite samples
courtesy of the Resident Geologist
Program, Ontario Ministry of Northern
Development and Mines. |
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Sandstone
Rock Type: sedimentary
Composition: grains of sand that
can be feldspar or quartz - the amount
of other minerals, such as mica, depend
on how much weathering has occurred.
Environment: Already existing
rocks are eroded and the grains are
transported and sorted by rivers. The
resulting sand is deposited on beaches,
along floodplains or in deltas, where it
is eventually buried by other sediments.
This causes a slow squeezing of the
sediments. As the sediments are
compacted, fine clay helps to fuse the
larger particles together. The sediments
are also cemented by chemicals left by
the water in the original sediment. The
presence of sandstone indicates that
there was water with fairly high energy
(waves on a beach or a fast moving
river)
Distinguishing Characteristics:
Coarse to very fine grains, beige to
grey colour, feels like sandpaper.
Origin of your Samples:
Georgetown, Ontario
Uses: Sandstone is used for
flagstone to line your walkway or patio.
It is also an important building stone.
Sandstone samples
courtesy of Rice & McHarg Quarries Ltd. |
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Shale
Rock Type: sedimentary
Composition: grains of clay
Environment: Shale sediments are
deposited in still water (low energy)
such as a lake or a deep, slow river.
Distinguishing Characteristics:
dull, reddish- brown, very fine grains
(smooth to the touch), breaks easily. If
an edge is dipped in water and drawn
along a surface, shale will leave a
muddy streak.
Origin of your Samples: Aldershot,
Ontario
Uses: This shale is the raw
material for the brick manufacturing
industry in Ontario.
Shale samples courtesy
of Hanson Brick Ltd. |
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Slate
Rock Type: metamorphic
Composition: clay minerals
Original Rock: shale
Environment: Slate forms from the
heat and pressure when shale is buried
deep in the crust. The depth of burial
to make slate out of shale is about 10
km. The temperature at that depth is
about 200°C.
Distinguishing Characteristics:
dark grey to black, very fine grains
(smooth to the touch), harder than
shale, distinct layers are visible.
Origin of your Samples: Vermont,
USA
Uses: slate is used in flooring
and roofing materials. In the past,
slate was used as chalkboards.
Slate samples courtesy
of Heather and Little Ltd. |
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