Chapter 3

The following figure shows a sample of pyrite (FeS2). Which of the following statements can you verify simply by visual inspection of this sample? a. Pyrite has one plane of cleavage and is magnetic. b. Pyrite has a golden streak and a cubic crystal habit. c. Pyrite has metallic luster and a cubic crystal habit. d. Pyrite has nonmetallic luster and two planes of cleavage.

c. Pyrite has metallic luster and a cubic crystal habit. FEEDBACK: Luster and crystal habit are both observable in this specimen of pyrite. The luster speaks of the way the mineral scatters light. The crystal habit is the shape that euhedral crystals will take through unencumbered growth.

______ is a common mineral that can come in different colors, such as clear, milky, rose, and amethyst. a. Pyrite b. Halite c. Quartz d. Talc

c. Quartz

SiO4^4-, S^2-, and CO3^2- are all examples of a. organic compounds. b. silicate minerals. c. anions. d. cations.

c. anions.

The image below shows a mineral with hydrochloric acid applied to it. Based on the reaction and presence of gas bubbles, which of the following minerals is the most likely to be _______? a. quartz b. halite c. calcite d. fluorite

c. calcite

Gemstones are often found in pegmatites, which are igneous rocks that are a. exceptionally mafic. b. extrusive, forming from lava. c. exceptionally coarse-grained. d. exceptionally fine-grained.

c. exceptionally coarse-grained.

We distinguish between a mineral and a naturally formed glass (such as obsidian) because a. glass is not produced by geologic processes. b. glass is organic. c. glass does not have a fixed crystal structure. d. glass can be made synthetically as well as occur naturally.

c. glass does not have a fixed crystal structure.

Which of the following minerals is more commonly known as rock salt? a. gypsum b. feldspar c. halite d. quartz

c. halite

Which of the following describes the process of mineral dissolution? a. heating to a temperature where bonds between atoms break b. reacting minerals with reagents to form new minerals c. immersing in water such that atoms or ions separate from crystal faces d. breaking apart bonds to release chemical energy for microbes

c. immersing in water such that atoms or ions separate from crystal faces

Which common gemstone results from biomineralization? a. diamond b. garnet c. pearl d. sapphire

c. pearl

What type of silicate is the mineral mica? a. chain silicate b. framework silicate c. sheet silicate d. ring silicate

c. sheet silicate

Cleavage is the tendency of a mineral to break in a predictable manner when subjected to a force. The image below shows a calcite fragment. Which statement about calcite's cleavage is TRUE? a. Calcite has one plane of cleavage. b. Calcite has two perpendicular planes of cleavage. c. Calcite has two inclined planes of cleavage. d. Calcite has three planes of cleavage, one of which is inclined.

d. Calcite has three planes of cleavage, one of which is inclined. FEEDBACK: Calcite has three planes of cleavage. The sample, appears not cubic, but rhombohedral. This is because one of the three planes is inclined with respect to the other two.

The angles between adjacent crystal faces of the same type of mineral _______ a. are always the same. b. vary widely among different specimens of the mineral. c. depend on the size of the crystal. d. are 90° for every type of mineral.

a. are always the same.

The image below shows the atomic structure of a graphite crystal. The hexagons are made by strong covalent bonds, while the sheets are held together by much weaker Van Der Waal forces. Based on this information and the shape of the structure, how many planes of cleavage could graphite be a. one plane b. two planes c. three planes d. no planes

a. one plane FEEDBACK: Graphite has one plane of cleavage. The mineral is much more likely to break the weak Van Der Waal forces holding the sheets to one another than to break the strong within-sheet covalent bonds. When a graphite pencil is used to draw a line, it leaves behind tiny sheets of graphite on the paper.

When two different minerals have the same chemical formula but different crystal structures, they are said to be a. polymorphs. b. polyliths. c. monoliths. d. pseudomorphs.

a. polymorphs.

The mineral class that makes up more than 95% of the continental crust is termed the a. silicates. b. carbonates. c. halides. d. oxides.

a. silicates.

The classes of silicate minerals differ from one another based on how the Si-O molecules are linked to each other. The image below shows many of the different arrangements. What shape is the base silicon-oxygen molecule that makes up these different arrangements? a. tetrahedron b. hexahedron c. octahedron d. decahedron

a. tetrahedron FEEDBACK: The base silica tetrahedron comprises one silica atom surrounded by four oxygen atoms. The tetrahedral chains, rings, and sheets are made when tetrahedra share oxygen atoms.

Using the Mohs hardness scale below, which of the following statements about the actual hardness of minerals is false? a. Your fingernail can scratch a sample of gypsum. b. Diamonds are twice as hard as apatite. c. Diamonds are more than seven times as hard as quartz. d. Quartz will scratch anything made of steel.

b. Diamonds are twice as hard as apatite.

Which tool is used to detect the pattern of atoms in a crystal? a. magnetic resonance imaging (MRI) b. X-ray diffraction c. thermal ionization mass spectrometry (TIMS) d. cathodized axial tomography (CAT)

b. X-ray diffraction

Of the ~4,000 known minerals, the vast majority ___________ a. are common. b. are rare. c. form only near volcanoes. d. are characterized as gems.

b. are rare.

Hardness refers to a mineral's ability to resist a. breaking. b. being scratched. c. chemically reacting with other substances. d. weathering.

b. being scratched.

If a mineral lacks cleavage, it will a. break along planar surfaces with specific orientations. b. break along irregular or conchoidal fractures. c. not break apart unless melted. d. not break apart unless dissolved.

b. break along irregular or conchoidal fractures

The tendency for minerals to break along distinct planar surfaces that have a specific orientation in relation to the crystal structure is called a. fracture. b. cleavage. c. specific gravity. d. hardness.

b. cleavage.

Which of the following choices lists atomic particles ordered from smallest to largest in size? a. atom, nucleus, proton, electron b. electron, proton, nucleus, atom c. proton, electron, nucleus, atom d. atom, electron, nucleus, proton

b. electron, proton, nucleus, atom

What type of silicate is the mineral quartz? a. chain silicate b. framework silicate c. sheet silicate d. ring silicate.

b. framework silicate

The shape of single crystals or aggregates of many well-formed crystals is known as: a. streak b. habit c. luster d. cleavage

b. habit

Chemical bonding is responsible for many of the physical properties we observe in minerals. The following figure shows one such bond type. Please choose the correct name for the chemical bond shown. a. metallic bond b. ionic bond c. covalent bond d. hydrogen bond

b. ionic bond

Diamonds are usually found in a rock called a. graphite. b. kimberlite. c. gabbro. d. diorite.

b. kimberlite.

What is solid-state diffusion? a. cooling of a liquid and turning it into a solid b. movement of atoms through a solid to form a new mineral c. bonding of dissolved ions into a solid crystal d. growth of a mineral within or adjacent to a living organism

b. movement of atoms through a solid to form a new mineral

The atomic number of an element corresponds to the __________ a. number of electrons. b. number of protons. c. number of neutrons. d. total weight of one atom.

b. number of protons.

The atomic mass of an element approximately equals the number of a. electrons. b. protons plus neutrons. c. neutrons. d. protons.

b. protons plus neutrons.

To correctly identify a mineral, geologists run several tests to gather information about the mineral's physical and chemical properties. Which test method is being demonstrated in the following figure? a. luster b. streak c. crystal habit d. cleavage

b. streak

Crystals grow outward from a central seed or nucleation point until they encounter interference from other crystals. If they do not encounter other crystals, they become large and well-formed. What type of crystal is being formed by the limited growth shown in the image below? a. euhedral b. subhedral c. anhedral d. trihedral

b. subhedral FEEDBACK: The central crystal was only able to grow a small amount before it encountered other crystals that limited its growth. Crystals that fill in voids or are limited from growing well-formed crystal faces are by definition anhedral.

Minerals in geodes (as seen below) form spectacular euhedral crystals because a. all of the elements incorporated in the crystals are in plentiful supply. b. the crystals have abundant room to grow in their hollow surroundings. c. minerals within geodes are always framework silicates. d. minerals within geodes always contain iron.

b. the crystals have abundant room to grow in their hollow surroundings.

Mineral crystals come in many different shapes. The image below shows a halite crystal. Which of the following statements regarding the mineral's characteristics is FALSE? a. Halite has cubic crystal habit. b. The atoms within Halite molecules are held together by chemical bonds. c. Halite has one strong plane of cleavage. d. Halite has sodium and chlorine ions in its chemical formula.

c. Halite has one strong plane of cleavage.

Minerals are all naturally occurring solid substances with a definable chemical composition. They must also possess a. the ability to be synthesized in the laboratory as well as be found in nature. b. metallic elements, such as iron, calcium, or magnesium. c. metallic luster. d. a fixed crystalline structure (spatial arrangement of atoms and ions).

d. a fixed crystalline structure (spatial arrangement of atoms and ions).

Diamond and graphite are both polymorphs of a. silicon. b. iron. c. magnesium. d. carbon.

d. carbon.

The quartz in this figure shows a very specific type of breakage. It is not cleavage. What is this type of break called? a. concave fracture b. irregular fracture c. iiInternal fracture d. conchoidal fracture

d. conchoidal fracture FEEDBACK: Conchoidal fracture is the smooth curved break that commonly results when glass chips. Our ancestors used the conchoidal fracture in quartz, obsidian, and flint to fashion early tools, knives, and arrowheads.

Crystals that exhibit well-formed faces are referred to as a. pristine. b. anhedral. c. subhedral. d. euhedral.

d. euhedral.

In silicate minerals, the SiO4 tetrahedron can be linked together by sharing: a. silicon atoms. b. cations. c. electrons. d. oxygen atoms.

d. oxygen atoms.

On the Mohs hardness scale, quartz has a hardness of 7 and calcite has a hardness of 3. This means that _______. a. calcite can scratch quartz b. quartz is four times harder than calcite c. calcite is four times harder than quartz d. quartz can scratch calcite

d. quartz can scratch calcite

Pyrite (FeS2) is in which mineral class? a. silicates b. carbonates c. oxides d. sulfides

d. sulfides

Crystal habit, such as needle-like, platy, or cubic, depends on _________ a. the color of the mineral's streak. b. the class the mineral belongs to. c. the wavelength of light reflected off the mineral surface. d. the mineral's growth rate in different directions.

d. the mineral's growth rate in different directions.