| A | B |
|---|
| molten rock | magma |
| decaying plant and animal material | humus |
| durable artificial rock | concrete |
| smells like mud when it is wet | shale |
| used in pencils instead of lead | graphite |
| used to make chalkboards | slate |
| person who studies minerals | mineralogist |
| hardest substance of all | diamond |
| rocklike object with crystals on the inside | geode |
| most useful metal | iron |
| rarest gemstone | ruby |
| only metal that is liquid at room temperature | mercury |
| best conductor of electricity | silver |
| substance that forms a special kind of solid called a crystal | mineral |
| a radioactive metal used as a source for nuclear power | uranium |
| lightweight, rustproof metal | aluminum |
| scientist who studies the structure of the earth | geologist |
| two types of weathering | chemical and physical |
| rare, beautiful minerals that are very hard but have not yet been polished | gemstones |
| oil in its natural state | petroleum |
| underground spring that shoots streams of boiling water into the air | geyser |
| person who explores caves | spelunker |
