CHAP 3: Matter + Minerals *
What is the difference between ionic, covalent, and metallic bonds?
1) Ionic bonding - atoms gain or lose outermost (valence) electrons to form ions. Ionic compounds consist of an orderly arrangement of oppositely charged ions. 2) Covalent bonding - atoms share electrons to achieve electrical neutrality. Covalent compounds are generally stronger than ionic bonds. Both ionic and covalent bonds typically occur in the same compound (bonds are seldom 100 percent ionic or covalent in character). 3) Metallic bonding - valence electrons are free to migrate among atoms. Weaker and less common than ionic or covalent bonds.
Suppose you found a mineral crystal that looked like topaz. What two minerals could you use in a scratch test to help determine if the mineral is indeed topaz?
Corundum and quartz
Name the hardest and softest mineral on the Moh's scale.
Diamond (hardest) and talc (softest)
What minerals make up half of Earth's crust?
Feldspars
Which of the following exhibits three sets of cleavage at 90° angles?
Galena
What is the basic foundation of Moh's hardness scale?
If a mineral scratches an object, then the mineral is harder than the object.
__________ SiO4 4- tetrahedra join with __________ ions to produce the mineral olivine in the rock peridotite.
Independent; Mg2+ and Fe2+
A mineral is naturally occurring, has an orderly internal structure, has a well-defined chemical composition, and is inorganic. What is is NOT?
It is not organic
Since color is not a very useful way to identify a mineral, what other optical property or properties can be used?
Luster and streak
What are minerals? (5)
Naturally occurring Inorganic Solid Ordered internal molecular structure Definite chemical composition
What are ores? What are common ores of iron and lead?
Ore is a useful metallic mineral that can be mined at a profit. Must be concentrated above its average crustal abundance. Profitability may change because of economic changes. Common Ores of Lead would be: Galena, which contains 86 percent Common Ores of Iron are: Hematite (Hematite deposits are the most important source of Iron Ore in the United States.)
What are the two most abundant elements in Earth's crust?
Oxygen and silicon
What is the most abundant mineral group in the Earth's crust?
Silicates
Which of the following best describes the term streak?
The color of a powdered form of a mineral produced by rubbing it across a hard surface.
What is an accurate description of the silicon-oxygen tetrahedron?
The silicon-oxygen tetrahedron is a four-sided figure with a silicon atom in the middle bonded to four neighboring oxygen atoms.
The mineral fluorite is an example of?
a halide mineral.
While studying some sedimentary rocks in your field area, you find a mineral with rhombohedral cleavage that reacts with hydrochloric acid. You determine that this mineral is:
calcite.
Quartz exhibits __________.
conchoidal fracture
In the field, you find an unidentified mineral that is clear, exhibits conchoidal fracture, and can scratch glass. This mineral is most likely:
quartz.
The principal mineral used in making glass is?
quartz.
Hardness describes a mineral's __________.
resistance to being scratched
The micas (biotite and muscovite) exhibit what type of silicate structure?
sheet
In silicate minerals, the type of cleavage or fracture is influenced by?
the bonding of the silicon-oxygen tetrahedra within the mineral.
Hornblende has _____ cleavage planes at _____ angles.
two; non-90°
The silicon-oxygen tetrahedron contains?
one silicon atom and four oxygen atoms.
What are some of the physical properties of minerals?
1) Luster - appearance of a mineral in reflected light Two basic categories: • Metallic • Nonmetallic - Other terms are used to further describe luster such as vitreous, silky, or earthy 2) Color - generally an unreliable diagnostic property to use for mineral identification. Often highly variable for a given mineral because of slight changes in mineral chemistry. Exotic colorations of some minerals produce gemstones. 3) Streak - color of a mineral in its powdered form. Helpful in distinguishing different forms of the same mineral. 4) Hardness - resistance of a mineral to abrasion or scratching. All minerals are compared to a standard scale called the Mohs scale of hardness. 5) Cleavage - tendency to break along planes of weak bonding. Produces flat, shiny surfaces. Described by resulting geometric shapes: number of planes and angles between adjacent planes. 6) Fracture - absence of cleavage when a mineral is broken 7) Specific gravity - ratio of the weight of a mineral to the weight of an equal volume of water. Average value is approximately 2.7. Other properties - Magnetism - Reaction to hydrochloric acid - Malleability - Double refraction - Taste - Smell - Elasticity
How are minerals different from rocks?
A rock is a solid aggregate or mass of minerals. Rocks are composed of minerals.
What causes the same mineral to occur in varieties that are different colors?
A small amount of impurities in the crystal structure.
What causes a lack of cleavage in some minerals?
Bonds of equal strength in all directions
What mineral is not scratched by a fingernail, but is scratched by a copper penny?
Calcite
Which of the following best describes the term cleavage?
Cleavage is the splitting of minerals along natural planes of weakness.
What are the eight elements that make up most of the Earth's crust?
Composed mainly of the 8 elements that make up more than 98 percent of the continental crust: oxygen 46.6% silicon 27.7% aluminum 8.1% iron 5.0% calcium 3.6% sodium 2.8% potassium 2.6% magnesium 2.1% The feldspars are the most common silicate group and make up more than 50 percent of Earth's crust. Quartz is the second-most abundant mineral in the continental crust and the only common mineral made completely of silicon and oxygen.
The ratio of silicon to oxygen atoms in silicate minerals depends on?
how the atoms in silicon-oxygen tetrahedra are shared.
The arrangement of the silicon-oxygen tetrahedra in ferromagnesian (iron- and magnesium-bearing) silicate minerals is typically?
in a chain.
The external expression of a mineral's orderly internal arrangement of atoms is referred to as?
its crystal form.
The amount or quality of light that is reflected from a mineral surface is known as __________.
luster
The property of cleavage reflects?
mechanical breakage along planes of weakness within the mineral.
