earth science 205 ch 3 reading quiz

How many planes of cleavage does this mineral have?

1. Minerals that "peel" off in thin sheets have one plane of cleavage. This separation is similar a stack of papers. Each piece of paper is stacked in the same plane, just as the sheets of mica in the image appear to be stacked.

The figure shows a sample of pyrite (FeS2). Which of the following statements can be determined to be true simply by visual inspection of this sample?

Pyrite has metallic luster. Luster and crystal habit are both observable in this specimen of pyrite. Luster refers to the way a mineral scatters light, and in the case of pyrite the luster is metallic. The crystal habit is the shape that euhedral crystals take during unencumbered growth. Pyrite has a cubic crystal habit.

The quartz in this figure shows a very specific type of breakage. What is this type of break called?

conchoidal fracture. Conchoidal fracture is the smooth curved break that commonly results when glass (which has no crystal structure) or a mineral with equally strong bonds in all directions (like quartz) chips. Our ancestors used the conchoidal fracture of quartz, obsidian, and flint to fashion early tools, knives, and arrowheads.

Asbestos was widely used as a fireproofing insulation. Why is it no longer used?

When inhaled it can embed in the lungs and cause cancer. Asbestos refers to a group of silicate minerals that grow in thin fibers. Breathing asbestos can embed fibers in the lungs and cause cancer. Asbestos does not give off toxic lead, pollute groundwater, or cause burns. It is only dangerous when inhaled.

Referring to the figure, would either of these rock samples be considered crystalline?

Yes, (b) is crystalline. Crystalline rocks form when minerals grow together and interlock. They can be igneous, sedimentary, or metamorphic, but are not clastic with cement. Crystalline rocks are common in outcrops.

Calcite that constitutes clamshells is an example of which method of mineral formation?

biomineralization. In this case, the minerals calcite and aragonite are formed biologically by the organism (the clam). Ice is an example of a mineral formed from the solidification of a melt, halite is an example of one precipitated from a solution, and minerals in metamorphic rocks are examples of those formed by solid-state diffusion.

The migration of atoms or molecules through a material is called

diffusion. Minerals can form by precipitation, biomineralization, solidification (freezing) from a melt, and diffusion. Diffusion is the name for the migration of atoms or molecules through a material.

The mineral crystals of amethyst growing into the center of the geode in the figure are

euhedral. Euhedral crystals grow unimpeded. The large crystals in the center of the geode are euhedral. Anhedral crystals are constrained by the space available. Tetrahedral and cubic refer to particular crystal shapes.

According to the Mohs hardness scale,

gypsum is softer than fluorite. According to the Mohs hardness scale, quartz and calcite are harder than talc, and diamond is about 10 on the scale. Gypsum is softer than fluorite.

What physical property of a mineral describes the shape of a cluster of many well-formed crystals that grew together as a group?

habit. Crystal habit is the geometry of a euhedral (well-formed) crystal or group of such crystals. Cleavage and fracture describe the way a mineral breaks. Hardness is a measure of a mineral's resistance to scratching.

The gemstones amethyst (a form of quartz), topaz, diamond, and sapphire (a form of corundum) all have this property in common.

harder than glass

Glass is not considered a mineral because

it does not have a crystal structure. Although glass is an inorganic solid with a definable chemical composition, it forms too quickly to have a crystal structure. Therefore, it is not considered a mineral.

Which of the following would be best used to study rocks in the field?

magnifying glass. Although a simple device for magnification, a hand lens would be most useful to study rocks in the field. A petrographic microscope and electron microprobe provide greater magnification, and a mass spectrometer permits precise measurements of atomic ratios, but all would be used in a lab.

Which of the following is a mineral?

salt (NaCl). Of the choices, only salt (halite) is a mineral. Amber is organic and not crystalline, and saltwater and oil are not solids.

Rocks that form at or near the Earth's surface by the cementing of grains or precipitation from water are

sedimentary. Sedimentary rocks form at or near the Earth's surface in two ways: by the cementing of rock grains or the precipitation of minerals from water. Igneous rock forms by the freezing (solidification) of molten rock. Metamorphic rocks form when rocks undergo mineral and textural changes but remain in a solid form. Bedrock is a term for rock near the surface but can be any of the three types of rock.

The most abundant mineral group on the Earth is the

silicates. The silicate group is the most abundant mineral group in the Earth's crust and mantle. The basic building block of silicate minerals can link in multiple configurations, forming hundreds of different chemical compounds.

When a mineral specimen is scraped along a ceramic plate to observe the color of its powder, the physical property being checked is

streak. Luster refers to how a mineral reflects light. Cleavage and fracture refer to its manner of breakage. Specific gravity refers to its density. The streak of a mineral is the color of the mineral when powdered. The color of a mineral specimen can vary greatly depending on impurities and the way that light interacts with the mineral, but the color of the streak should be uniform for all specimens of that mineral.

The image shows a calcite fragment. The calcite has

three planes of cleavage. Calcite has three planes of cleavage, with one of the three planes inclined with respect to the other two.

Diamonds are very hard gemstones that form

when carbon is subducted to 100 or more kilometers of depth. Diamonds form when graphite is subjected to very high-pressure conditions inside the Earth. Diamonds are not biomineralized like pearls or precipitated from water.

Why would brick not be considered a rock?

Bricks are human-made. Bricks are not considered rocks because they are manufactured and are not naturally occurring. Rocks must be solid and can be widely used in building. Rocks may have more than one mineral present but must not be human-made.

Why was asbestos used in brake pads?

It has a high melting temperature. Asbestos was used in brake pads because it can get very hot without melting. Engaging the brake of a moving car creates a great deal of friction between the car's brake pad and rotor, which generates a large amount of heat. The presence of asbestos insured a longer life for the brake pad.

___________ rocks form when existing rocks are subjected to high temperatures and pressures that cause changes in mineralogy and texture but do not melt.

Metamorphic. Metamorphic rocks form when existing rocks are subjected to high temperatures and pressures beneath the Earth's surface or in the Earth's interior. They differ from igneous rocks in that they remain solid and do not melt whereas igneous rock forms by the solidification (freezing) of molten rock. The high temperatures and pressures cause mineral and textural changes in the original rock, creating metamorphic rock.