Rocks & Minerals
The hardest known mineral
Diamond
Any hollow space in earth's crust that has formed naturally and is large enough for a person to enter.
Cave
The most commonly used practical metal
Iron
Any trace of a plant or animal left in a rock.
Fossil
Small deposits of igneous and metamorphic crystals
Gemstones
Thin, hollow tubes that hand from the ceiling of a cave
Soda straws
A metal that is a good conductor of electricity; two of its alloys are brass and bronze.
Copper
A hard, shiny, black coal; expensive to mine
Anthracite
Any rock containing a metal together with impurities
Ore
Cave formations that occur when layers of calcium carbonate build up around a grain of sand in a shallow pool.
Cave pearls
The area surrounding a magnet in which the force of the magnet affects other objects
Magnetic Field
The most common type of coal, also known as "soft coal"
Bitumious
The rarest, most durable and beautiful gems.
Precious stones
Cave formation that builds up from the cave floor due to dripping water containing calcium carbonate
Stalagmite
The ends of a magnet
Poles
The poorest quality of coal, also known as "brown coal"
Lignite
The hardest material that composes the earth's crust
Rock
A thicker icicle-shaped formation that hangs from the cave ceiling.
Stalactite
The magnetic field produced by the earth
Magnetosphere
The thick, dark, flammable liquid; considered a liquid fossil fuel
Petroleum