Difference between revisions of "Quartz"
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| − | Quartz. ___ Specimens mounted on illuminated Board. | + | ''Quartz.'' ___ Specimens mounted on illuminated Board. |
Crystals in the trapezohedral-hemihedral class of the rhombodhedral division of the hexagonal system. This class possesses neither planes nor center of symmetry, but only axes of symmetry. There are three uniterminal dyad axes of symmetry. Usually, however, this lower degree of symmetry is not indicated by the faces developed on the crystals. | Crystals in the trapezohedral-hemihedral class of the rhombodhedral division of the hexagonal system. This class possesses neither planes nor center of symmetry, but only axes of symmetry. There are three uniterminal dyad axes of symmetry. Usually, however, this lower degree of symmetry is not indicated by the faces developed on the crystals. | ||
Latest revision as of 20:25, 31 March 2008
Quartz
mi;1997.727;sp:
Quartz. ___ Specimens mounted on illuminated Board.
Crystals in the trapezohedral-hemihedral class of the rhombodhedral division of the hexagonal system. This class possesses neither planes nor center of symmetry, but only axes of symmetry. There are three uniterminal dyad axes of symmetry. Usually, however, this lower degree of symmetry is not indicated by the faces developed on the crystals.
Before the advent of electricity, farmers and those caring for livestock in rural areas placed rocks bearing quantities of quartz crystals toward the top of their stone walls and fences, to be used as guides in dim light; these minerals being noticeably easier to see at dusk than the dark gray mica-schist which is the usual composition of the Green Mountain range’s ledge table.
Quartz crystals are easily noticeable in a field, in the moonlight.
