NAME _________________________________________
DATE ___________ PER _____ DOC ____
Properties of Minerals
A mineral is a naturally occurring, inorganic solid that has a crystal structure and a definite
chemical composition. For a substance to be considered a mineral, it must have all five of these
characteristics. Geologists have identified more than 3,000 different minerals. Of these, only about 100
are common. About 20 minerals make up most of the rocks of Earth’s crust. These minerals are known
as rock-forming minerals. To be classified as a mineral, a substance must occur naturally in Earth’s crust.
A mineral must also be inorganic. This means that the mineral cannot arise from materials that were
one part of a living thing. A mineral is always a solid, with a definite volume and shape. The particles of
a mineral line up in a pattern that repeats over and over again. The repeating pattern of a mineral’s
particles forms a solid called a crystal. All minerals have a characteristics crystal structure. A mineral
has a definite chemical composition- it always contains certain elements in definite amounts. An
element is a substance composed of a single kind of atom. The vast majority of minerals are
compounds. In a compound, two or more elements are combined so that the elements no longer have
distinct properties. Some elements occur in nature in a pure form. These, such as silver and gold, are
considered to be minerals.
Each mineral has its own specific properties that can be used to identify it. The Mohs
hardness scale ranks ten minerals from softest to hardest. The color of a mineral can be used to identify
minerals that always have their own characteristic color. The streak of a mineral is the color of its
powder. Even though the color of a mineral may vary, its streak does not. Another simple test is a
mineral’s luster, the term used to describe how a mineral reflects light from its surface. Each mineral
has a characteristic density. No matter what the size of a mineral sample, the density of that mineral
remains the same. The crystals of each mineral grow to form that mineral’s particular crystal shape.
Geologists classify these shapes into six groups according to the number and angle of the faces. The way
a mineral breaks apart can help to identify it. A mineral that splits easily along flat surfaces has the
property called cleavage. Most minerals do not split apart evenly. Instead they have a property called
fracture. Fracture describes how a mineral looks when it breaks apart.
Some minerals can be identified by special properties. Minerals that glow under ultraviolet light
have a property known as fluorescence. Magnetism occurs naturally in a few minerals, such as
magnetite. Uraninite and a few other minerals are radioactive. Calcite gives off carbon dioxide when a
drop of vinegar is placed on it. A few minerals, such as quartz, have electrical properties.
Directions: Fill in the blanks in the table below.
Mineral Property
Test for the Property
1
Color
Observe surface of mineral
2
Scratch tests
3
Luster
4
Observe color of powder on unglazed tile
5
Find mass per volume
6
Crystal structure
7
The way a mineral breaks apart
8. What are the five characteristics necessary for a substance to be a mineral?
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9. Each mineral has its own unique properties that are different from every other mineral because each
mineral has only one _______________________________________________________.
10. List five special properties of minerals that make certain minerals easier to identify.
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Directions: Match each term with its definition.
____________ 11. cleavage
a. the property of glowing under ultraviolet light
____________ 12. streak
b. how a mineral reflects light from its surface
____________ 13. luster
c. a substance composted of a single kind of atom
____________ 14. compound
d. the property of splitting evenly along flat faces
____________ 15. fluorescence
e. two or more elements chemically combined
____________ 16. fracture
f. how a mineral breaks unevenly
____________ 17. Mohs hardness scale
g. repeating pattern of a mineral’s particles
____________ 18. crystal
h. the color of a mineral’s powder
____________ 19. element
i. ranking of minerals from 1 to 10