Graphology - the study of handwritings; autograph - written with one's own hand; seismograph - a machine noting strength and duration of earthquakes. marina - a harbor for pleasure boats; maritime - relating to the sea; submarine - an undersea boat; aquamarine - color of sea water.
Chemicals are classified into various hazard classifications in accordance with their physiochemical properties and health hazards. Each class of chemical has a pictorial symbol called a danger symbol.
**Minerals and gemstones are classified according to their chemical compositions. There are eight classes, along with a ninth class for non-minerals, which may be non-crystalline organic combinations and/or rocks. The nine classes are listed below with examples of a few of the individual species within these groups.