EofG Ch3

Glass is not a mineral because it doesn't have crystal lattice structure. a. True b. False Section: 3.2, p. 73; Figure 3.3(b), p. 73

A Feedback/Reference: By definition, a mineral has a crystal lattice structure; glass doesn't have this structure.

A mineral can exist in a crystal lattice framework or as glass, an amorphous solid. a. True b. False Section: 3.2, p. 73

A Feedback/Reference: By definition, minerals are crystalline; because glass is amorphous (lacks crystalline structure) it is not a mineral.

Which of these statements is the most accurate statement about conchoidal fracture? a. It occurs in minerals that have one to three directions of cleavage. b. Halite has conchoidal fracture. c. Only carbonates and sulfates can have conchoidal fracture. d. Jewelers who are faceting diamonds attempt to find and break diamonds in conchoidal patterns. e. Mineral crystals that break in curved surfaces are exhibiting conchoidal fracture. Section: 3.4, p. 79

A Feedback/Reference: Conchoidal fracture is the curved manner is which glass breaks. Most minerals have cleavage (break in planar [flat] surfaces), and quartz is the most familiar mineral that breaks conchoidally instead of by cleavage.

When you scrape a mineral along a ceramic plate to observe the color of its powder, you are checking the physical property known as a. streak. b. luster. c. cleavage. d. specific gravity. e. fracture. Section: 3.4, p. 78

A Feedback/Reference: Luster is how something handles light; cleavage and fracture refer to the manner of breaking; specific gravity refers to density.

Ore minerals are often sulfides and oxides of metallic elements. a. True b. False Section: 3.5, p. 81

A Feedback/Reference: Many metallic elements bond with sulfur and oxygen in the environment to produce sulfides and oxides.

Gold and copper can both be found as native metals. a. True b. False Section: 3.5, p. 81

A Feedback/Reference: Metals that exist as elements, not compounds, are called native metals; gold and copper are two examples.

Mica peels apart in parallel sheets because the chemical bonds between sheets are weak and the chemical bonds within sheets are strong. a. True b. False Section: 3.4, p. 79; Figure 3.9(a), p. 82

A Feedback/Reference: Mica has perfect cleavage in one direction because chemical bonds within each layer are strong but bonds between layers are weak.

An unknown mineral scratches glass, has only average specific gravity, and shows no cleavage but does show conchoidal fracture. Which of the following could it be? a. quartz b. talc c. halite d. mica e. galena Section: 3.4, pp. 78-79

A Feedback/Reference: Only quartz meets these specifications; talc is too soft, halite and mica have excellent cleavage, and galena has a high specific gravity.

The Hope Diamond, now in the Smithsonian Institution in Washington, D.C., is exceptional because in addition to being the subject of legends and curses, it is a blue diamond. a. True b. False Section: 3.6, p. 83; Figure 3.11, p. 85

A Feedback/Reference: Pale color of a diamond diminishes its value; strong color, such as the blue color of the Hope Diamond, increases its value.

Minerals generally can be destroyed by heating, dissolution or other chemical reaction. a. True b. False Section: 3.3, pp. 76-77

A Feedback/Reference: Probably every mineral known can be destroyed by heating, dissolution or reaction with specific chemicals. Metamorphism is a process that breaks down nearly all minerals under geologically-occurring conditions of changed temperature, pressure or presence of other chemicals.

An unknown mineral sample can be scratched by a copper penny and will scratch the penny. It reacts with dilute hydrochloric acid to produce carbon dioxide gas. Which of the following could it be? a. calcite b. fluorite c. talc d. gypsum e. None of the above. Section: 3.4, p. 77-79; Table 3.1, p. 81; Figure 3.8(f), p. 80

A Feedback/Reference: The unknown mineral has a hardness of three, but the most specific and useful property in classifying it is reaction with dilute hydrochloric acid. This property and its hardness fit calcite.

Examples of precious stones are diamonds, rubies, sapphires, and emeralds; examples of semiprecious stones are aquamarines, garnets, topaz, and tourmaline. a. True b. False Section: 3.6, p.84

A Feedback/Reference: These are all good examples of very valuable precious gemstones and less valuable semiprecious gemstones.

The mineral bronze is produced when humans melt copper and tin together. a. True b. False Section: 3.2, p. 72

B Feedback/Reference: A mineral must be naturally occurring.

The energy of various crystals has been shown by scientists to improve human health. a. True b. False Section: 3.3, p. 73

B Feedback/Reference: Although crystals are sometimes attributed mystical powers, scientists have not demonstrated that they can improve human health or exude special energies.

Which of the following groups of silicate minerals exhibits a single strong cleavage in one direction? a. framework silicates b. sheet silicates c. independent tetrahedra silicates d. single-chain silicates e. double-chain silicates Section: 3.5, p. 82

B Feedback/Reference: Atomic bonding between the sheets is weak, so they separate easily in this direction.

Calcite and halite both have one direction of cleavage. a. True b. False Section: 3.4, p. 79; Figure 3.9, p. 82

B Feedback/Reference: Both have three cleavage directions. In halite, they're at right angles; in calcite, they're not.

Facets are created by jeweler's and exploit directions of weakness that exist because of crystalline structure. a. True b. False Section: 3.6, p. 85; Figure 3.12, p. 93

B Feedback/Reference: Facets are produced by a jeweler's tool. Facets may lie along crystal faces and cleavage planes, though skilled jewelers can create facets that do not correspond to cleavage planes.

Which of the following is a mineral? a. amber (tree sap) b. ice c. sugar (formula C6H12O6) d. ivory (from animal tusks) e. coral (from reefs) Section: 3.3, p. 76

B Feedback/Reference: Ice fits the mineral definition criteria; amber, sugar, coral, and ivory have organic origins.

All precious and semiprecious stones must be transparent. a. True b. False Section: 3.6, p. 84

B Feedback/Reference: Lapis, malachite, and opal are semiprecious stones that are opaque or translucent.

Color and cleavage are two very useful physical properties used to identify quartz. a. True b. False Section: Figure 3.8(a), p. 78

B Feedback/Reference: Quartz can come in various colors and shows no cleavage.

Identify the FALSE statement: Diamonds a. are brought from the mantle to the surface in magma that hardens into kimberlite. b. are brought through the crust in large carrot-shaped structures called pegmatites. c. of industrial quality are used as abrasives. d. that have weathered out of ore bodies can end up in stream gravels. e. have been found in South Africa, India, northwest Canada, and the Rocky Mountains in the United States. Section: Box 3.2, p. 84

B Feedback/Reference: The carrot-shaped structures in which diamonds are found are called kimberlite pipes

A geode is filled with anhedral crystals on its walls. a. True b. False Section: 3.3, p. 77; Figure 3.7, p. 79

B Feedback/Reference: The crystals had room to grow well-developed crystal faces and therefore are euhedral.

There are two physical properties of minerals that both result in smooth, flat surfaces with specific angles between them. The first property is the result of how the mineral forms; the second is the result of breaking a sample of the mineral. These properties are called, respectively, a. hardness and cleavage. b. cleavage and hardness. c. crystal habit and cleavage. d. cleavage and crystal habit. e. crystal habit and hardness. Section: 3.4, pp. 79, Figure 3.9, p. 82

C Feedback/Reference: Crystal habit is the geometry of a euhedral (well-formed) crystal; cleavage describes the way a mineral breaks. Hardness is a measure of a mineral's resistance to scratching.

Identify the FALSE statement: a. There is an angle of 120° between each crystal face of the hexagonal column of a quartz crystal. b. Crystals can be a variety of geometric shapes, including cubes, trapezoids, pyramids, octahedrons, hexagons, columns, blades, needles, and obelisks. c. Negative ions (cations) have more protons than electrons; positive ions (anions) have more electrons than protons. d. The faces of a crystal need not be the same size throughout the crystal, but the angle of intersection between comparable faces is the same throughout. e. Crystals have symmetry. Section: Box 3.1, p. 74

C Feedback/Reference: Negative ions are anions, and they have more electrons than protons. Positive ions are cations, and they have more protons than electrons.

The tendency of a mineral to break and produce smooth, curving shell-shaped surfaces is termed a. luster. b. fibrous fracture. c. conchoidal fracture. d. streak. e. perfect cleavage. Section: 3.4, p. 79; Figure 3.9(f), p. 82 Resources: Flashcards

C Feedback/Reference: Only conchoidal fracture matches the definition given.

Identify the FALSE statement: Formation of table salt Topic: n/a a. is, in mineralogic terms, formation of the halide halite. b. takes place when a solution has become saturated. c. is an example of solidification of a melt. d. needs a seed crystal to begin. e. results in cubic crystals. Section: 3.3, p. 76

C Feedback/Reference: Salt is an example of precipitation from a solution.

Identify the FALSE statement: Crystals a. have an orderly internal arrangement of atoms patterned as if attached to an imaginary framework called a crystal lattice. b. grow outward from a seed. c. are formed by the high-temperature, extremely rapid process known as solid-state diffusion. d. display symmetry. e. cause X-ray diffraction. Section: 3.3, p. 73

C Feedback/Reference: Solid-state diffusion is the very slow migration of atoms through solid material as they rearrange themselves on a crystal lattice. It occurs in metamorphic rocks.

What do mica and graphite have in common? a. Both are silicate minerals. b. Both have three directions of cleavage. c. Both are semiprecious stones. d. Both break in one preferential direction. e. Both react with hydrochloric acid (HCl) to "fizz" (bubble and produce carbon dioxide). Section; 3.4, p. 79

D Feedback/Reference: Although micas are a family of minerals, both micas and graphite break prominently in one direction.

Graphite is a. the polymorph of galena. b. harder than glass. c. pure silicon. d. the lead in the pencil you write with. e. composed of carbon atoms, arranged as tetrahedrons, and held together with strong covalent bonds. Section: 3.3, pp. 75 - 76; Figure 3.6 (a)(b), p. 78

D Feedback/Reference: Graphite is the very soft, pure carbon polymorph of diamond. Its carbon atoms are arranged in sheets, weakly bonded to each other.

Calcite is a mineral that can constitute oyster shells, and, in such cases, is an example of which method of mineral formation? a. solidification of a melt b. precipitation from a solution c. solid-state diffusion d. biomineralization e. fumerolic mineralization Section: 3.3, p. 84

D Feedback/Reference: In this case, the calcite is formed biogenically by the living oyster. Most minerals form abiogenically (without involvement of biological systems). Calcite can also be precipitated from a solution, this would be considered an abiogenic way of forming it.

The expression 24 karat must mean that a. you're talking about the biggest diamond ever found. b. the gemstone is flawed by impurities. c. there are 24 cleavage planes present. d. the gold is 100% pure. e. the gold weighs 24 ounces. Section: Box 3.2, p. 84

D Feedback/Reference: Karat is a measure of purity; 24 karat means a gold item is 100% gold (see Box 3.2, Where Do Diamonds Come From).

Which mineral group composes more than 95% of the minerals of the continental crust? a. carbonates b. sulfates c. sulfides d. silicates e. sulfates and sulfides when considered as one group Section: 3.5, p. 81

D Feedback/Reference: Silicates make up the majority of the entire crust and approximately 95% of the continental crust, but are rare to absent within Earth's core.

Which is NOT a physical property commonly used in the lab or field to identify minerals? a. color b. streak c. luster d. diffraction e. specific gravity Section: 3.4, p. 78

D Feedback/Reference: These easily observable physical properties are: color, streak, luster, hardness, specific gravity, crystal form, crystal habit, cleavage, and special properties. X-ray diffraction, is a sophisticated procedure used to examine crystal lattice patterns.

Silicates a. have the silicon-oxygen tetrahedron as their structural unit. b. are a major component of continental crust. c. are classified on the basis of how the tetrahedrons join and share oxygen atoms. d. are a huge category of minerals and include the common minerals quartz and feldspar. e. All the possible answers are correct. Section: 3.5, pp. 81-82; Figure 3.10, p. 83 Resources: Flashcards

E Feedback/Reference: All the possible answers are correct.

For which of the following reasons is the methane within natural gas not a mineral? a. It's naturally occurring. b. There may have been biological processes involved in its formation. c. It has a specific composition. d. It is formed by geologic processes. e. It lacks a crystalline structure. Section: 3.2, p. 73

E Feedback/Reference: Each choice is true except for "lacks a crystalline structure." Gases and liquids are not solids and therefore are not minerals.

Why are cleavage and habit often confused? a. They both exhibit an identical and otherwise unique pattern when examined by X-ray diffraction. b. They both relate to the chemical destruction of minerals. c. They are both terms for conchoidal fracture. d. Both are exhibited strongly by sulfides but not other mineral families. e. Both can result in a mineral crystal having planar sides. Section: 3.4, p. 79

E Feedback/Reference: Habit is the three-dimensional shape that a mineral crystal will grow into under ideal conditions, whereby cleavage is how a mineral crystal will break.

Which of the following is NOT a mineral? a. glacial ice, because ice isn't a rocky material b. salt, because it's not crystalline c. a gold nugget, because it's a native metal d. pyrite, because it's a chemical compound e. oil, because it's a liquid, not a solid Section: 3.1, p. 72

E Feedback/Reference: Minerals by definition must be solid. Also, they don't have to be rocky material. Salt is crystalline. The descriptions of gold and pyrite are correct, but these are not disqualifying reasons.

Which of these is a special property that is NOT useful in differentiating most minerals from one another? a. cleavage b. streak c. hardness d. habit e. magnetism Section: 3.4, p. 77

E Feedback/Reference: Only a very few minerals are magnetic, hence this property is generally not of use in classifying most minerals.

Which pair of minerals listed below are polymorphs? a. calcite and dolomite b. quartz and halite c. graphite and mica d. diamond and topaz e. graphite and diamond Section: 3.3, p. 76

E Feedback/Reference: Polymorphs have identical chemical compositions but different crystallographic structures. Graphite and diamond are both carbon but have differing crystallographic structures, as well as being on opposite ends of the Mohs scale of hardness.

Ice crystals form by solidification of a melt. a. True b. False Section: 3.3, p. 76

a Feedback/Reference: Ice is the solid crystal form of the liquid (or melt) form of water.