Unit 28: Minerals and Igneous Rocks
Teacher Questions
1) Generally, the ____ it takes for a mineral to form, the _____ the size of the crystal (mark
all that is true).
a) longer; larger *
b) shorter; larger
c) longer; smaller
d) shorter; smaller *
2) Diamonds and graphite are composed of the exact same element, carbon, but both
differ significantly in hardness. Which statement is NOT true with regard to their
hardness?
a) graphite atoms are arranged in sheets and are held together by weak bonds
b) diamonds are arranged in a tetrahedral crystalline structure
c) diamonds are held together by very strong bonds
d) the color differences help to determine the hardness of each mineral *
3) Imagine working in the field and discovering a mineral that looks like a diamond. Which
common mineral could you use to determine if the mineral was a valuable diamond or a
common quartz crystal by performing a scratch test? Refer to Moh’s hardness scale
(Table 28.X).
a) Calcite
b) Gypsum
c) Apatite
d) topaz *
4) Atom is to molecule, as element is to _____.
a) electron
b) proton
c) mineral *
d) rock
5) Which mineral is a silicate mineral?
a) quartz *
b) calcite
c) halite
d) gypsum
6) As the rate of cooling decreases, crystal size ____.
a) decreases
b) increases *
c) stays the same
d) increases and then decreases
7) Obsidian:
a) cools slowly and has a glassy appearance
b) cools rapidly and forms one large crystal
c) cools slowly and forms large crystals
d) cools rapidly and has a glassy appearance *
8) Granite and gabbro
a) have similar coarse grained texture *
b) have similar mineral composition
c) have similar composition but different texture
d) are not similar at all
9) The following pictures depicts this type of weathering property:
http://www.nps.gov/depo/photosmultimedia/Devils-Postpile.htm#
a) exfoliation
b) lithifaction
c) columnar jointing *
d) erosive dome
10) As a volcanologist, you are responsible for mapping a volcanic field. You understand
that the size of a crystal is related to its rate of cooling. You found an outcrop with rocks
made up of coarse-grained crystals set within a fine-grained matrix like a chocolate chip
cookie. The chocolate chips would be relative to the coarse-grained crystals and the
cookie itself would represent the fine-grained matrix. Plate the following statements in
order of its occurrence.
a) As dissolved gasses continue to precipitate out of the magma solution, pressure
builds (3)
b) Lava quickly cools forming the fine-grained matrix (5)
c) Magma chamber buried deep beneath surface undergoing slow rate of cooling (1)
d) Pressure becomes so great that the magma erupts onto the surface (4)
e) Because magma is less dense than the surrounding country rock, it continues to rise
expelling dissolved gasses (2)
11) Laccoliths are:
a) large discordant structures that bulge in a dome-like manner
b) vertical layers that cut through rock layers
c) a massive pluton assimilating surrounding rock structures
d) an intrusive body forming between rock layers pushing overlying rock upwards *