The extreme hardness of diamond is explained by all atoms being bonded
covalently.
a lack of cleavage.
a
conchoidal fracture pattern.
chemical
composition; carbon atoms are very difficult to scratch.
If gemstone A is the same size, shape (cut) and weight as gemstone B then we may
conclude thata) gemstone A and B are the same
materials.
b)
gemstone A and B have the same specific gravity.
c)
gemstone A is an imitation of gemstone B.
d)
they are both of equivalent value.
e)
a and b.
If cubic zirconia has a higher specific gravity than that of diamond, then identically
cut and faceted diamond and cubic zirconia gemstones will weigh the same
amount because they are cut the same.
weigh
different amounts; the diamond will be heavier.
weigh different amounts; the cubic zirconia will be heavier.
weigh
different amounts, but which is heavier will depend on how big they are.
weigh the same amount because they have very similar physical properties.
Crystalline materials differ from amorphous materials by a) containing
different chemical elements.
b) having periodic spacing of atoms.
c) being natural rather than man-made.
d) a and b.
e) all of the above.
Step-cut gemstones can be distinguished from brilliant-cut gemstones bythe
shapes of the facets.
the size of the table.
whether the crown is domed or flat.
the strength of the play-of-color.
the number of facets; brilliant cuts have more facets than step cuts.
Conchoidal fracture iscommon in minerals that contain 2
cleavages.
common in minerals that contain 1 cleavage.
common in minerals that do not have a cleavage.
a fracture pattern that looks like splintered wood.
restricted to minerals that have high specific gravities.
Cleavage and parting are two physical properties that affect a gem or mineral'sa)
toughness
b) hardness
c) durability
d) a and c
e) all of the above.
A Mohs hardness of 7 is often considered the minimum for jewelry gemstones because
softer gemsa) break too easily.
b) can't be polished.
c) are too easily scratched.
d) a and c
e) all of the above.
Which of the following is correctly arranged by hardness? Corundum, topaz,
orthoclase, quartz
Fluorite, orthoclase, quartz, topaz.
Quartz, corundum, topaz, diamond.
Diamond, corundum, quartz, topaz.
Talc, gypsum, fluorite, calcite.
A gemstone that floats on top of a heavy liquid has a specific gravity that is the
same as the liquid.
greater than the liquid.
less than the liquid.
greater than or less than the liquid, depending on size of the gemstone.
none of the above
A mineral's luster is a physical property that depends on the diffraction of
light from the mineral's surface.
the reflection of light from the minerals surface.
the absorption of different wavelengths of light at the minerals surface.
the presence or absence of a chromophore.
the emission of light after some light is absorbed.
Asterism is caused bythe presence of more than one
chromophore.
randomly arranged, reflective mineral inclusions.
color centers.
diffraction in more than one direction.
none of the above
Tiger's eye or gems that display a cat's eye exhibit a phenomenon calledasterism
chatoyance
play-of-color
aventurescence
none of the above
To see the green color in an emerald, the Cr present must absorb the green
part of the visible spectrum.
yellow part of the visible spectrum.
red
part of the visible spectrum.
blue part of the visible spectrum.
part of the infrared spectrum.
Gem labradorite feldspar and opal owe their unique color displays toaventurescence.
color centers.
fluorescence.
transition metal chromophores.
diffraction
Play-of-color is a term used to describedifferent colors caused by many
different chromophores.
the difference between hue and tone.
flashes of color in opal.
aventurescence in sunstone.
a particularly vibrant Broadway show.
Aventurescence is a phenomenon caused byreflective mineral inclusions.
fluorescence in moonstone.
diffraction.
color centers.
none of the above
Fluorescence of a gem in ultraviolet light is a result ofthe emission of
ultraviolet light.
dispersion.
diffraction.
the absorption of visible light.
the absorption of ultraviolet light and the emission of visible light.
Color in allochromatic minerals and gems is a diagnostic property that can aid in
mineral or gem identification.
caused by chromophores that are present in great abundance.
not a diagnostic property for identification purposes.
caused by reflection from randomly arranged mineral inclusion.
none of the above.
Color centers are the source of color in minerals thatcontain transition elements.
are ideochromatic.
are capable of diffracting light.
contain crystal lattice defects.
are fluorescent.
Absorption of light by chromophores to produce color occurs within the nucleus
of the chemical element that is the chromophore.
by moving a proton from one type of orbital to another.
when atoms can move from one site to another within a crystal, absorbing energy.
by the movement of electrons.
by diffraction.
Transition elements are uniquely suited to act as chromophores because theycontain
electrons in partially filled d-orbitals.
are electrically neutral.
are the most common elements in nature.
are highly mobile in crystals.
all of the above.
A gem or mineral that is red absorbs red light.
mostly red light.
most wavelength of the visible spectrum except red.
more of the visible spectrum than a gem or mineral that is violet.
less of the visible spectrum than a colorless gem.
Gems and minerals whose color can be altered by high energy forms of radiation are
colored bycolor centers
diffraction
transition elements
play-of-color
none of the above
In crystallography, a form is defined asthe habit of the mineral.
a group of symmetrically related crystal faces.
a group of crystal faces with adjoining edges.
a specific type of symmetry element.
an incomplete crystal.
The internal arrangement of atoms in crystalline materials is reflected in the external
shapes of crystals by the angles between crystal faces.
the symmetry of crystal faces.
the shape of the smallest, imaginary "building block" needed to
construct the crystal.
all of the above.
The symmetry of crystal faces with respect to a line, plane and/or point can be used to
classify crystals into crystal habits.
closed or open crystal forms.
crystal interfacial angles.
crystal systems.
none of the above.
The hexagonal crystal system differs from all others in being composed of a unit cell
thathas 4 imaginary axes.
has a long c-axis.
is smaller than all the others.
has sides that are not at right angles.
has 6 faces.
The isometric (cubic) crystal system has having3 crystallographic axes of
equal length.
4 crystallographic axes of unequal length.
no crystallographic axes perpendicular.
no crystallographic axes of equal length.
3 crystallographic axes of unequal length.
Minerals that form crystals that fall within the tetragonal crystal system canalso
form crystals of the isometric system.
grow crystals of different shapes, but all the crystals will have symmetries of
the tetragonal system.
also form crystal that have symmetries appropriate to any of the crystal
systems.
show nearly an infinite variety of symmetries.
have only a center of symmetry.
Most common gem minerals are members of the isometric, tetragonal and
hexagonal crystal systems
monoclinic and triclinic systems
orthorhombic and isometric systems
isometric system
orthorhombic system
Prism and pinacoids are types of open forms
crystalline solids
symmetry operators
crystallographic axes
closed forms
Hue is the term used to describe the amount of brown or gray present in a
color
vibrancy of a color
color present (red, blue, green, etc.)
darkness or lightness of the color
none of the above.