mineral groups

sulfates

Sulfate minerals contain sulfur atoms bonded to four oxygen atoms, just like silicates and phosphates. Like halides, they form where salt water evaporates. The most common sulfate mineral is probably gypsum (CaSO4 (OH)2 ) (Figure 1.9). Some gigantic 11-meter gypsum crystals have been found (See opening image). That is about as long as a school bus! Gypsum.

textbook_image

sulfides

Sulfides are formed when metallic elements combine with sulfur in the absence of oxygen. Pyrite (Figure 1.10) (FeS2 ) is a common sulfide mineral colloquially known as "fools gold" because it has a golden metallic looking mineral. There are three easy ways to discriminate real gold from fools gold: real gold is extremely dense, real gold does not grow into perfect cubes, as pyrite commonly does, and pyrite smells like rotten eggs (because of the sulfur). Click image to the left or use the URL below. URL:

textbook_image

mineral groups

Minerals are divided into groups based on chemical composition. Most minerals fit into one of eight mineral groups.

halides

Halide minerals are salts that form when salt water evaporates. Halite is a halide mineral, but table salt (see Figure bond with various metallic atoms to make halide minerals. All halides are ionic minerals, which means that they are typically soluble in water. Two carbonate minerals: (a) deep blue azurite and (b) opaque green malachite. Azurite and malachite are carbonates that contain copper instead of calcium. Beautiful halite crystal.

textbook_image

textbook_image

carbonates

The basic carbonate structure is one carbon atom bonded to three oxygen atoms. Carbonates consists of some cation (like C, Fe, Cu, Mg, Ba, Sr, Pb) bonded to a carbonate molecule. Calcite (CaCO3 ) is the most common carbonate mineral (Figure 1.4). Calcite.

textbook_image

phosphates

Phosphate minerals are similar in atomic structure to the silicate minerals. In the phosphates, phosphorus bonds to oxygen to form a tetrahedron. As a mineral group they arent particularly common or important rock-forming minerals, but they are important for you and I. Apatite (Figure 1.8) is a phosphate (Ca5 (PO4 )3 (F,OH)) and is one of the major components of human bone!

textbook_image

oxides

Oxides contain one or two metal elements combined with oxygen. Many important metal ores are oxides. Hematite (Fe2 O3 ), with two iron atoms to three oxygen atoms, and magnetite (Fe3 O4 ) (Figure 1.7), with three iron atoms to four oxygen atoms, are both iron oxides. Magnetite is one of the most distinctive oxides since it is magnetic.

textbook_image

silicate minerals

The roughly 1,000 silicate minerals make up over 90% of Earths crust. Silicates are by far the largest mineral group. Feldspar and quartz are the two most common silicate minerals. Both are extremely common rock-forming minerals. The basic building block for all silicate minerals is the silica tetrahedron, which is illustrated in Figure 1.1. To create the wide variety of silicate minerals, this pyramid-shaped structure is often bound to other elements, such as calcium, iron, and magnesium. Silica tetrahedrons combine together in six different ways to create different types of silicates (Figure 1.2). Tetrahe- drons can stand alone, form connected circles called rings, link into single and double chains, form large flat sheets of pyramids, or join in three dimensions. One silicon atom bonds to four oxygen atoms to form a silica tetrahedron. The different ways that silica tetrahedrons can join together cause these two minerals to look very different.

textbook_image

textbook_image

native elements

Native elements contain atoms of only one type of element. Only a small number of minerals are found in this category. Some of the minerals in this group are rare and valuable. Gold (Figure 1.3), silver, sulfur, and diamond are examples of native elements.

textbook_image

instructional diagrams

No diagram descriptions associated with this lesson

questions

which of these is the largest of the mineral groups?

a) carbonates

-->  b) silicates

c) halides

d) oxides

these minerals are salts that form when salt water evaporates.

a) carbonates

b) silicates

-->  c) halides

d) oxides

the most common minerals are quartz and feldspar.

-->  a) true

b) false

halides are covalent minerals so they are soluble in water.

a) true

-->  b) false

fools gold can easily be distinguished from real gold because

-->  a) fools gold is more dense than gold

b) real gold does not grow in perfect cubes like fools gold

c) fools gold reacts with acid

d) all of the above

hematite is iron oxide, which is a form of rust.

-->  a) true

b) false

which of these is not a characteristic of minerals in the carbonate group?

a) the basic structure is one carbon atom bonded with three oxygen atoms.

b) a cation is bonded to the basic carbonate structure.

c) these minerals can be very colorful.

-->  d) calcium is nearly always part of the carbonate mineral structure.

silicate minerals are made up of

a) calcium, iron and magnesium in any number bonded with silica in a pyramid shape.

b) one silicon atom bound to three oxygen atoms to form a geometric shape.

-->  c) silica tetrahedra, which may be bound to other elements.

d) silica pyramids, which are bound only to each other, but in different structures.

which of the following descriptions of a mineral group is not true?

a) sulfate minerals contain sulfur atoms bonded to four oxygen atoms.

b) sulfide minerals are formed of a metal combined with sulfur, but no oxygen.

-->  c) phosphate minerals have a similar atomic structure to carbonates with one cation and

d) oxides contain one or two metal ions combined with oxygen.

the silicate structure can be combined in different shapes to form different minerals.

-->  a) true

b) false

diagram questions

No diagram questions associated with this lesson