Concept #6 Quiz

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Concept #6 Quiz
Choose the best possible answer to the following questions about Key Concept 6 "The Si-O tetrahedron and silicate minerals."

This activity contains 12 questions.

All silicate minerals have the same fundamental building block, the SiO₄ tetrahedron (see figure). Which of the following is not a way in which this building block makes silicate minerals?

Individual tetrahedra bond with cations to form "island" silicates like olivine.Bonds into sheets to form mica.Bonds into three-dimensional networks to form feldspar.Bonds into diamond shapes to form minerals like quartz.

	In a silicon-oxygen structural unit, silicon atoms occupy the corners of a tetrahedron. (See figure for question 1.)
	True False

Why does the ratio of Si to O vary from silicate mineral to silicate mineral?

Each tetrahedron is separate from every other tetrahedron in a silicate mineral, so the ratio varies only if tetrahedra are bonded with extra Si atoms.Each tetrahedron bonded to another tetrahedron does so by sharing an O atom, so the more sharing, the lower the ratio of Si-O.Some tetrahedra bond with cations by losing an O atom.Each tetrahedron is separate from every other tetrahedron in a silicate mineral, so the ratio varies only if tetrahedra are bonded with extra O atoms.

Which cations bond most often with Si-O tetrahedral structures in silicate minerals?

Fe, Mg, Ti, PCa, K, Al, SiFe, Mg, Ca, NaFe, K, Al, O

Many silicate minerals, like olivine and plagioclase, are actually a family of minerals within the silicate mineral group. What about them makes them that way?

They have nearly identical chemical compositions and identical physical properties.They are the same mineral, but different varieties.They have the same name, but their properties are all different.They have different chemical compositions and some similarity in physical properties.

As shown in the figure, different silicate minerals are grouped based upon how Si-O tetrahedra bond. In this grouping scheme, three-dimensional network silicate minerals have either no cleavage (quartz) or two planes of cleavage at 90 degrees (feldspar). What causes this difference within the same silicate group?

Unlike quartz, the feldspars have no cations in their atomic structure, allowing cleavage.Unlike the feldspars, quartz has Al and some combination of Na, Ca, and K in its atomic structure, allowing fracture.Unlike the feldspars, quartz has Al in its atomic structure, causing fracture.Unlike quartz, the feldspars have Al and some combination of Na, Ca, and K in their atomic structure, allowing cleavage.

The study of a silicate mineral’s atomic structure and chemical composition permits geologists to draw inferences upon which of the following?

The continent on which it was formed.The environment in which it was formed.The order in which it was formed.The time at which it was formed.

Why are “light” silicates much less dense than the “dark” silicates?

They have Na and Ca in them.They do not have Fe or Mg in them.They do not have Ca or Na in them.They have Fe and Mg in them.

Each mineral in the feldspar group is very similar to each other in terms of physical properties. What is the only reliable visible difference between potassium feldspar and plagioclase?

Plagioclase has characteristic cleavage.Potassium feldspar has characteristic color.Plagioclase has characteristic "striations."Potassium feldspar has characteristic hardness.

Muscovite and biotite are in the same silicate mineral group due to their extreme similarity (the micas; sheet silicates). What is the only significant difference between them?

Muscovite has one cleavage plane, biotite has two.The mineral’s major anions.Different hardness and luster.The mineral’s major cations.

Match the following silicate mineral groups with the inferred process of formation:

Using the pull-down menus, match each item in the left column to the corresponding item in the right column.


	product of higher-temperature igneous rock crystallization

	product of chemical weathering (phase change), an important component of soil

	a product of lower-temperature igneous rock crystallization, or metamorphism, and is resistant to weathering so is found in many sedimentary rocks.

11.1 clay minerals

11.2 olivine

11.3 quartz

What minerals form by the breakdown and weathering of rock-forming silicate minerals and are important constituents of soils?

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