1. To be
considered a mineral, a substance must exhibit the following
characteristics: (1) be naturally
occurring, (2) be a
solid, (3) have an orderly crystalline structure, (4) have a
definite chemical composition, and (5) generally be inorganic.
2. A
rock is a more or less hardened (lithified) aggregate
of minerals and/or amorphous solids, such as natural glass and organic matter.
3. The
particles are electrons, protons, and neutrons. The latter two are heavy
particles found in the nucleus of an atom. Electrons are tiny, very lightweight
particles that form a “cloud” surrounding the nucleus. The mass and charge data
are as follows:
proton—one atomic mass
unit, +1 electrical charge
neutron—one atomic mass
unit, electrically neutral
electron—tiny
fraction of one atomic mass unit, –1 electrical charge
4. (a) The number of protons—a neutral atom with 35 electrons
has 35 protons. (b) The atomic number— the
atomic number is 35, equal to the number of protons in the nucleus. (c) The number of neutrons—the
mass number (80) is the sum of protons (35) and neutrons. Thus the nucleus
contains 45 (80 – 35) neutrons.
5. Isotopes
of an element have varying numbers of neutrons in the nucleus and, hence, different
atomic weights.
6. An
ion is produced when an atom gains or loses one or more electrons and becomes
either negatively charged (if electrons are gained) or positively charged (if
electrons are lost).
7. Crystal
form refers to the geometrically regular, external growth shape that minerals
can exhibit if crystal growth is free and unobstructed by other minerals (the
crystal grows into a fluid-filled cavity, for example). Most crystal growth in
nature is obstructed (not free), so crystals showing their characteristic,
geometric forms are uncommon.
8. Impurities often cause the same mineral to have many colors. For example, fluorite can be purple, clear, or yellow, and quartz can be practically any color.
9. The
hardness test might help you make a determination, since diamond is the hardest
mineral in nature.
10. Any mineral listed on the Mohs scale (Figure 2.12), corundum for example, will scratch softer minerals (those with lower hardness values) and will not scratch harder minerals. Corundum will scratch virtually all other minerals, diamond being the lone exception. Thus corundum is widely used in abrasives and polishing compounds.
11. The specific gravity of water is 1 by definition. Thus the weights
of equal volumes of water and gold will be in the ratio 1:20. Because 5 gallons
of water weighs 40 pounds, 5 gallons of gold will weigh almost 800 pounds (5
gallons x 160 pounds/gallon = 800 pounds).
12. The two most abundant elements in Earth's crust (by weight) are
oxygen (46.6%) and silicon (27.7%). The basic building block of all silicate
minerals is the silicon–oxygen tetrahedron.
13. Feldspars are by far the most plentiful group of silicate minerals,
constituting more than 50 percent of Earth's crust. Quartz is the second most
abundant mineral in the continental crust.
14. Three nonsilicate minerals that are
commonly found in rocks are calcite, halite, and gypsum.
15. Mineral reserves are identified deposits from which minerals can be
extracted profitably. A mineral resource has a broader definition. In addition
to including reserves, it also includes known deposits that are not yet
economically or technologically recoverable, as well as deposits that are
inferred to exist but have not yet been discovered.
16. One way a mineral deposit can become profitable to extract is
through an economic change (e.g., the demand for a metal may increase and cause
a price increase). Also, if a technological advance allows the metal to be
extracted at a lower cost, it may become profitable to extract and thus be
reclassified as an ore.
Answers
to the Earth System Questions
1. (Answers
will vary depending on the mineral commodity selected)
2. (Answers
will vary depending on the mineral commodity selected)