OPAL: The Virgin Valley opal fields of Humboldt County in northern Nevada produce a wide variety of precious black, crystal, white, fire, and lemon opal. The black fire opal is the official gemstone of Nevada.
science Rock Cycle - When picking rocks for hardscapes use Metamorphic rock, especially with water (so it doesn't leach anything into water) also important to know what type of rockscape animals may have evolved in.
Petoskey stone is a rock and a fossil, often pebble-shaped, that is composed of a fossilized coral. The stones were formed as a result of glaciation. Petoskey was the state mineral of Michigan during the