Ch 2 - Minerals

Describe this mineral's cleavage:

This mineral has cleavage in 1 direction.

Which statement is true about the cleavage of this specimen? This specimen is exhibiting cleavage in 4 directions.

This specimen does not exhibit cleavage; it has fracture. Volcanic glass is an example of a rock that is not made up of minerals. Glass is produced when molten rock "freezes" so quickly that its constituent atoms do not have time to arrange themselves into an orderly crystal structure. You can read more about volcanic glass on page 66 in Chapter 3. Since volcanic glass has no crystal structure, it does not cleave. Instead, it breaks in an irregular way, so it is said to fracture. Volcanic glass shows a specific type of fracture called conchoidal fracture (its fractured surface is smooth and curved like the inside of a clam shell).

If you have a clear piece of this mineral and place it over some text, you will see a double image of each letter.

calcite

This mineral will produce bubbles if acid is applied to it.

calcite

Minerals that break in characteristic ways due to the presence of planes of weak bonding within the crystal structure are said to have this property.

cleavage

Match each mineral below with one of its important uses. See Table 1.2 on page 21 in your lab manual if you need help. a. magnetite b. sulfur c. gypsum d. quartz e. galena f. fluorite g. calcite h. chalcopyrite

a. iron ore; used to make steel b. sulfuric acid, sulfa drug c. wallboard, plaster d. glass e. ore of lead f. prevents tooth decay g. cement; lime; chalk h. copper ore, used to make wiring

True or False? True A lab-created emerald is a mineral.

false

The shape of a naturally-formed mineral crystal is a product of chance; it is not a characteristic that is helpful for identifying the mineral.

false On the contrary, the outward shape of a crystal is the result of the orderly arrangement of atoms at the microscopic scale within the crystal. See Figure 2.2 in the textbook; Slide 10 in the Chapter 2 PowerPoint states that the faces of a crystal are arranged precisely (not randomly) in relation to one another.

True or False? Orthoclase feldspar is harder than quartz.

false Orthoclase feldspar has a hardness of 6 and quartz has a hardness of 7, so quartz scratches feldspar (quartz is harder than feldspar).

True or False? The Mohs' Scale of Hardness is only useful for the 10 minerals listed on the scale.

false You can test any mineral's hardness and determine its position on the Mohs' Hardness Scale.

Minerals that have bonds that are equally strong in all directions usually break in an irregular way and are said to have this property.

fracture

A mineral-like material that has been melted and cooled so quickly that ions are "frozen in place" and do not form an orderly crystal structure.

glass

This mineral has a "greasy" feel and will make a mark on paper.

graphite

You can scratch the mineral gypsum with your fingernail.

gypsum Gypsum (hardness = 2) is softer than your fingernail (hardness about 2.5), so your fingernail will scratch it.

This mineral tastes salty (note: tasting minerals in your kit is not recommended).

halite

This is a measure of the resistance of a mineral to abrasion or scratching.

hardness

This specimen of volcanic glass is not a mineral.

is not use image for 19 & 20

Color (is / is not) the most reliable physical property of minerals because ________________.

is not, small amounts of impurities in a mineral like quartz produce a wide variety of possible colors for this mineral.

This is a description of the way in which light is reflected from the surface of a mineral. The two most important categories are metallic and non-metallic.

luster

This mineral reflects light like a metal; it exhibits metallic luster .

luster You can read about the luster of minerals on pages 42-43 in the textbook.

This mineral will attract a magnet.

magnetite

A naturally-occurring, inorganic solid with an orderly crystal structure and well-defined chemical composition.

mineral

Are usually formed from aggregates of minerals although they are sometimes formed from non-mineral matter.

rock

This is the ratio of a mineral's weight to the weight of an equal volume of water.

specific gravity

This is the color of the powdered mineral, usually produced by rubbing the mineral against a porcelain plate.

streak

Although real gold and fool's gold (pyrite) both have a yellowish metallic luster, they can be distinguished by their streaks . Although real gold will make a golden mark on the porcelain plate, pyrite will make a greenish-black streak .

streaks; makes a greenish-black streak

This mineral is very soft and feels "soapy."

talc

True or false? Gold sinks to the bottom of a miner's pan because it has a high specific gravity.

true

True or False? True Table salt (pictured below) is a mineral.

true -use the image for 4-6

True or False? False Glacial ice is a mineral.

true Table salt, aka halite, is a mineral. Since the emerald is man-made, it does not fit our definition of a mineral. As discussed in the Chapter 2 PowerPoint, ice fits the definition of a mineral; this would include glacial ice.