Rock identification
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Transcript Rock identification
ROCK IDENTIFICATION LAB
What type of rock is this? Where or how is it formed?
Obsidian
Mafic (black) Extrusive Igneous Rock
No crystals formed
Glassy
Very quick cooling molten rock (lava)
What type of rock is this? Where or how is it formed?
Basalt
Mafic Extrusive Igneous Rock
Fine grained (some small crystals)
Formed from dark dense lava
Pyroxene, plagioclase feldspar
What type of rock is this? Where or how is it formed?
Scoria
Mafic Extrusive Igneous Rock
No crystals formed
Forms as a frothy crust on the top of a
lava flow or as material ejected from a
volcanic vent and solidifying while
airborne
Many holes formed - gasses released
What type of rock is this? Where or how is it formed?
Pumice
Felsic Extrusive Igneous Rock
No crystals formed
Quick cooling molten rock (lava)
Many holes formed - gasses released
Floats on water
What type of rock is this? Where or how is it formed?
Granite
Felsic Intrusive Igneous Rock
Coarse Grained - can see crystals
Contains quartz and feldspar
What type of rock is this? Where or how is it formed?
Shale
Clastic Sedimentary Rock
Thin, dark gray sheets – easily broken
Formed from mud and clay being
pressed together
What type of rock is this? Where or how is it formed?
Image Source
Sandstone
Clastic Sedimentary Rock
Light red/dark pink with very small
pieces of sand
Quartz cemented by silica or lime
Most form in shallow seas
What type of rock is this? Where or how is it formed?
Image Source
Coal
Organic Sedimentary Rock
Black, smooth and lightweight
Formed from layers of plant remains
that are pressed together over time
What type of rock is this? Where or how is it formed?
Image Source
Limestone
Organic Sedimentary Rock
Calcium Carbonate - calcite
Forms from the accumulation of shell,
coral, and fecal debris in clear, warm,
shallow marine waters
What type of rock is this? Where or how is it formed?
Conglomerate
Clastic Sedimentary Rock
Red with rounded pebbles cemented
together
Formed near moving water
What type of rock is this? Where or how is it formed?
Quartzite
Metamorphic Rock
Non-Foliated
Individual quartz grains have
recrystallized but are too small too see
Metamorphism of Sandstone
What type of rock is this? Where or how is it formed?
Marble
Metamorphic
Non-Foliated
Made of mostly small to medium sized
calcite crystals
Metamorphism of Limestone
What type of rock is this? Where or how is it formed?
Gneiss
Metamorphic
Foliated – pink and grey alternating
bands
Medium to coarse grained texture
Metamorphism of Granite
What type of rock is this? Where or how is it formed?
Slate
Metamorphic Rock
Foliated
Breaks into thin “slices”
Metamorphism of Shale
What type of rock is this? Where or how is it formed?
Hornfels
Metamorphic Rock
Non-foliated
Fine grained crystals
Metamorphism of clays or Shales
Comparisons
Basalt vs. Slate
Both
dark colors
Basalt is igneous and Slate is metamorphic
Pumice vs. Basalt
Both
igneous made of quick cooling lava (extrusive)
Pumice is felsic and Basalt is mafic
Granite vs. Gneiss
Both
have course grains/crystals
Granite is igneous and Gneiss is metamorphic
Comparisons
Scoria vs. Pumice
Both
are porous (have air bubbles/holes)
Scoria is mafic and Pumice is felsic
Obsidian vs. Coal
Both
are black, no crystals
Obsidian is igneous and Coal is sedimentary
Marble vs. Limestone
Both
are made of calcite
Marble is metamorphic and Limestone is sedimentary
Comparisons
Slate vs. Shale
Both
thin slices, made of mud and clay, dark color
Slate is metamorphic (morphed from shale), Shale is
sedimentary
Hornfels vs. Slate
Both
metamorphic rocks made from Shale
Hornfels is not foliated and Slate is foliated
Sandstone vs. Quartzite
Both
grainy and made of Quartz
Sandstone is sedimentary and Quartzite is metamorphic
Comparisons
Limestone vs. Marble
Both
are made of calcite
Limestone is sedimentary and Marble is metamorphic
Conglomerate vs. Limestone
Both
sedimentary rocks formed in or near water
Conglomerate is clastic (made of pebbles cemented
together by moving water) and Limestone is organic
(made of shell coral, fecal debri found in shallow water)
Gneiss vs. Granite
Both
contain course grain crystals
Gneiss is metamorphic and Granite is igneous
Comparisons
Quartzite vs. Sandstone
Both
contain the mineral Quartz
Quartzite is metamorphic (pressure and heat),
Sandstone is sedimentary (cemented together by water
+ sandstone or lime)
Coal vs. Obsidian
Both
are black and smooth and contain no crystals
Coal is sedimentary and Obsidian is igneous
Shale vs. Slate
Both
made of mud and clay (Slate is made from Shale)
Shale is sedimentary and Slate is metamorphic