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

Image Source

What type of rock is this? Where or how is it formed?

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

Image Source

What type of rock is this? Where or how is it formed?

Coal

Organic Sedimentary Rock Black, smooth and lightweight Formed from layers of plant

remains that are pressed together over time

Image Source

What type of rock is this? Where or how is it formed?

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