Six Crystal Systems
Cubic System
Image not available.
Three axes of equal
length intersect at 90°
angles.
Examples:
Please refer to the
sylvite, halite
image in the textbook
or in the eEdition CD.
Sylvite
Orthorhombic System
Image not available.
Three axes, each of a
different length,
intersect at 90° angles.
Prefixes in words that describe
geometric shapes can often give you
clues to the words’ meanings. For
example, mono- means “one” and
clin means “incline.” Therefore,
monoclinic means “having one axis
at an inclined (oblique) angle.” In
tetragonal, tetra- means “four,” and
-gon means “angle.” Each face of a
tetragonal shape has four angles.
Examples:
Please refer to the
topaz, sulfur
image in the textbook
or in the eEdition CD.
Topaz
Tetragonal System
Image not available.
Three axes intersect at
90° angles. Two of the
axes are equal in
length.
Examples:
Please refer to the
wulfenite, zircon
image in the textbook
or in the eEdition CD.
Wulfenite
Triclinic System
Image not available.
Three axes, each of a
different length,
intersect at oblique
angles.
Please refer to the
image in the textbook Examples:
or in the eEdition CD. kyanite, turquoise
Kyanite
Hexagonal System
Image not available.
Three axes of equal
length intersect at 60°
angles. The fourth axis
(vertical) can be longer
or shorter than the
other axes.
Please refer to the
image in the textbook
or in the eEdition CD. Examples:
emerald, graphite
Monoclinic System
Image not available.
Emerald (a form of beryl)
Three axes, each of a
different length,
intersect, with two of
the intersections at 90°
angles and the third at
an oblique angle.
Please refer to the
image in the textbook
or in the eEdition CD. Examples:
gypsum, mica
Gypsum
Axes of equal length are shown in the same color.
Chapter 5 Atoms to Minerals
99