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ROCK TYPE / PROPERTIES
Characteristics of IGNEOUS Rock
(from molten rock or volcanic fragments)
Possible Textures:
Glassy
Vesicular (full of bubble holes)
Or randomly oriented small crystals or randomly oriented large crystals no
fossils or organic material.
Some Possible Chemistries: Dark colors (rich in magnesium or iron); multicolored
(several kinds of mineral crystals are present); light colors (rich in quartz or
feldspars); sometimes distinctive minerals are present such as olivine (green) or
alkali feldspar (pink).
Some
1.
2.
3.
Characteristics of SEDIMENTARY Rock
(from sediments or precipitation of crystals in water at or near Earth's
surface)
Some Possible Textures:
1. Clastic or made of rock fragments either large or small such as mud, silt,
sand, gravel or pebbles)
2. Parallel layers
3. Fragments of life forms (fossils)
Some Possible Chemistries:
4. Often one color (if fine grained);
5. Multicolored if composed of large rock fragments cemented together
6. Sometimes composed of calcite (precipitated by corals or shells) which
fizzes when acid is applied; sometimes composed of halite or gypsum
(soft light-colored crystalline rocks that form when salty water bodies dry up).
Characteristics of METAMORPHIC Rock
(from physical or chemical alteration of other rocks by heating or intense pressure beneath Earth's
surface)
Some Possible Textures:
1. Foliated (folds such that minerals lie parallel to one another)
2. Banded (separate bands of light and dark minerals make wavy folds in the
rock -- not like the flat layers in sedimentary rocks)
3. An especially shiny metallic reflection from crystals aligned parallel to one
another; may contain very large crystals of equal size; sometimes deformed
fossils (stretched or crushed).
Some Possible Chemistries: Often contain "metamorphic minerals" such as garnets (reddish-brown 12-sided
crystals), mica (flat and shiny gray), and epidote (light green).
Rock Type
Sedimentary
(layers &
earthy tones)
Rock Color
Rocks tend to be tan or grey in
color.
Rock Compositions
Layers visible when broken.
Composed of clays, fine grained but
not very smooth.
Unique Properties
When more heat and
pressure added
‘morphs’ into slate.
Shades of red, oranges, tans, or
whites in color. Generally 1 color
or layering may show different
shades.
Usually greys, tans or white in
color (Samples containing iron
are reddish). Generally 1 color.
Grainy/Sandy feeling. Visible
grains. Often have visible layers.
May contain fossils.
Nicknamed ‘Red Rock”
Sandstone
Medium to fine grained (may see
grains w/ naked eye). More coarse
to touch. May see layering.
Fizzes w/ HCL. May
contain fossils.
Limestone
Very fine grained (cannot see
grains). Composed of silts, muds &
clays. May feel chalky.
May contain fossils.
Not foliated (no layers). Medium
grained.
Medium to coarse grained. Hard
rock w/ interlocking quartz crystals.
Common parent rock is
limestone.
Parent rock is
sandstone.
Quartzite
Banding due to alternate layers of
different minerals, or different
colors.
Harder, denser and may be shinier
than shale.
Parent rock is often
granite.
Gneiss
Shades of tans, greys or creams.
Metamorphic
Cream or white in color. May
show swirls of darker color.
White, tan or pink.
Can be different colors, mostly
black and white, may contain
pink, green, or brown.
Shades of grey.
Rock Name
Shale
Siltstone
Parent rock is shale.
When tapped on
another rock has
higher pitch than shale.
Marble
Slate
Rock Type
Igneous
Extrusive
(no visible
crystals)
Intrusive
(large crystals)
Rock Color
Black, dark grey.
Rock Compositions
Glassy texture. No visible grains.
Volcanic glass. Fractures look like
broken glass.
Lighter colors of grey and
Very light rock with small to
brown.
medium sized holes. Sandpaper
feel.
Generally dark brown, black or
Fairly dense with small to medium
red.
sized holes.
Dark in color (blacks & greys)
Fined grain and more dense than
pumice or scoria. May contain very
small or no visible holes.
Generally lighter in color, usually
Large mineral grains of quartz,
mostly black and white
feldspar, hornblende and mica.
speckled, may also contain pink
or brown speckles.
Dark in color.
Large mineral grains of feldspar,
augite and olivine. No quartz
crystals.
Unique Properties
Conchoidal fracture
(breaks in a circular
pattern)
Will float in water.
Rock Name
Obsidian
Pumice
Will sink in water.
Makes up oceanic
plates.
Scoria
Basalt
Parent rock of gneiss.
Granite
Can be magnetic. Also
may contain rare
metals like platinum.
Gabbro
Name
Date
Period
Introduction: Rocks are records of past climates, life, and tectonic processes. In this lab you will describe the physical characteristics
of 8-10 rocks and use those characteristics to determine whether the rock is igneous, metamorphic, or sedimentary, its name, and its
environment of formation.
Part I: Rock Types and Names
Directions: Complete the table below describing each of your rock samples. Use your class notes, the Rock Type Properties Key, and
the Rock Names Key to determine which type of rock each sample is and its name. Justify your choices for each rock type and name by
citing characteristics of the sample that match characteristics in the keys in the evidence columns.
Rock
#
Drawing
Description
(Color(s), Texture, Crystal
presence,
size, & shape, unique
properties)
Type of Rock?
(Igneous,
Metamorphic,
Sedimentary)
Evidence
Rock Name
Evidence
Part II: Environment of Formation
Directions: Pick 3 of the rocks from your bucket. Research the environments in which these rocks form (Use your class notes,
textbook, or other resources). Explain how their characteristics show evidence of their environment of formation. One example has
been completed for you.
Rock Name
Mica Schist
Environment of Formation and Evidence
Flattened crystals and foliation indicate this rock was exposed to intense heat and pressure that caused
partial melting and rearrangement of its crystal grains.