COPPER (Cu) is a naturally occurring pure element with a
reddish-orange color.
This is the element copper in its pure natural form. The specimen, which is 5 cm long, shows the dendritic habit of copper. The gray material is gangue (wall rock) material consisting of calcite.
Copper has with very high electrical and thermal
conductivity, and the main uses for this soft element are for electrical wire,
plumbing parts, and industrial machinery. In order to make copper harder, it is
purposely combined (alloyed) with other metals:
brass = an alloy
of copper and zinc
bronze = an alloy
of copper and tin
cupronickel =
alloy of copper and nickel (used in making coins, like the U.S. nickel = 75%
copper and 25% nickel).
Copper is one of the few metals that occurs naturally as a
directly usable form. This led to its being used by early humans, as far back
as 9000–8000 BC. The discoveries of making alloys out of copper happened later
(e.g., the Bronze Age about 3700–100 BC).
Like aluminum, copper is readily recyclable without any loss
in quality. It has been estimated that 80% of all copper ever mined is still in
use today.
MOLYBDENITE (MoS2) is the mineral molybdenum sulfide, the principal source of the metallic element molybdenum. This high-temperature hydrothermal mineral is silvery/gray in appearance (similar to graphite = pencil "lead"), is greasy to the touch, and peels apart (in one direction) in somewhat heavy but flexible sheets.
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| This specimen of molybdenite is 4 cm long (from upper left to lower right). |
Molybdenite can withstand extreme temperatures without significantly expanding or softening. The element molybdenum readily combines with other elements and forms hard,
stable alloy materials, which are used for making high-strength steel. In particular, these alloys are used in military
armor, aircraft parts, electrical contacts, industrial motors, etc.
This specimen came from a quartz veinlet in granite at a commercial mine in Climax, Colorado.
