3. Mineral composition and structure:
Minerals composition and it structure are controlled by
several factors:
1.The relative abundances of available elements.
2.The relative sizes and charges of these elements atoms and
ions.
3.The temperature and pressure at the time of formation.
Minerals may have the same chemical composition but
different crystal structures because they formed under
different temperature and pressure conditions. For
example graphite and diamond that consist entirely of
carbon. Graphite’s structure forms under relatively low
pressure at shallow depths, whereas diamond’s structure
results from intense pressure at depth greater than 150
km.
Graphite
3
Diamond
4. The physical properties of minerals include:
Color: the color of the mineral.
Streak: the color of the mineral’s powder.
Luster: the way light reflects off the mineral’s surface.
Specific gravity: how heavy the mineral is relative to the same
volume of water.
Cleavage: the mineral’s tendency to break along flat surfaces.
Fracture: the pattern in which a mineral breaks.
Hardness: what minerals it can scratch and what minerals can
scratch it.
Physical Properties of minerals
5. Mineral Groups
• Minerals are divided into groups based on chemical
composition. Most minerals fit into one of eight mineral
groups.
• Silicate Minerals
• The roughly 1,000 silicate minerals make up over 90% of
Earth’s 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.
7. • 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, silver, sulfur, and
diamond are examples of native elements.
Gold (Au)
8. • Carbonates
• The basic carbonate structure is one carbon atom bonded to three
oxygen atoms. Carbonates include other elements, such as calcium,
iron, and copper. Calcite (CaCO3) is the most common carbonate
mineral (Figure below).
•
Calcite (CaCO₃)
9. • Halides
• Halide minerals are salts that form when salt water evaporates. Halite
is a halide mineral.
Halite (NaCl)
10. • Oxides
• Oxides contain one or two metal elements combined with oxygen.
Many important metals are found as oxides. Hematite (Fe2O3), with
two iron atoms to three oxygen atoms, and magnetite (Fe3O4)
(Figure below), with three iron atoms to four oxygen atoms, are both
iron oxides.
Hematite (Fe2O3)
11. • Phosphates
• Phosphate minerals are similar in atomic structure to the silicate
minerals. There are many different minerals in the phosphate group,
but most are rare (Figure below).
Turquoise is a phosphate mineral containing
copper, aluminum, and phosphorus.
12. • Sulfates
• Sulfate minerals contain sulfur atoms bonded to oxygen atoms. Like
halides, they form where salt water evaporates. The sulfate group
contains many different minerals, but only a few are common.
Gypsum (CaSO4⋅ 2H2O.)
13. • Sulfides
• Sulfides are formed when metallic elements combine with
sulfur. Unlike sulfates, sulfides do not contain oxygen.
Pyrite (FeS2)
