Jade:
A translucent gemstone consisting of either jadeite or nephrite that is typically green in color. Jade is a very durable stone and is used for a variety of jewelry and ornamental objects. Typically cut in the cabochon shape or carved.
Jadeite:
A high pressure clinopyroxene that is frequently carved and polished as a gemstone.
Jasper:
A variety of colored chert, typically red or green and often found in association with iron ores. Jasper is frequently used as a gemstone or in the production of ornaments.
Jet:
A variety of coal that is frequently cut and polished for jewelry or ornaments.
Jetty:
A human made structure built at right angles to a coastline and extending into the water. Jetties are built to protect an area of shoreline from the effects of currents, erosion or deposition.
Joint:
A fracture in rock along which there has been no displacement.
Joint Set:
A group of joints that are parallel or nearly parallel. They are frequently formed at the same time interval from a common process.
Jolly Balance:
A spring balance used in the determination of specific gravity.
Juvenile Water:
Water that is new to the hydrologic cycle. Brought to Earth's surface through volcanic eruptions.