Australites

Australites are small, button- or lens-shaped pieces of glass found in the southern part of... More >>

Emery

Emery, EHM uhr ee or EHM ree, is a hard black or gray rock that consists chiefly of the minerals... More >>

Geode

Geode, JEE ohd, is a hollow, stonelike formation often lined with crystals. Geodes are found in... More >>

Gravel

Gravel is a mixture of loose pieces of rock and particles of sand and clay. At least 30 percent... More >>

Metamorphism

Metamorphism, meht uh MAWR fihz uhm, is the set of processes by which rocks are changed in... More >>

Pudding stone

Pudding stone is a common term for a type of conglomerate stone consisting of rounded pebbles... More >>

Pumice

Pumice, PUM ihs, is a grayish-white natural glass with many tiny holes. It is a valuable... More >>

Quicksand

Quicksand is a soft mass of wet sand that yields easily to pressure. It usually forms on the... More >>

Rock

Rock is the hard mineral substance that forms the solid part of Earth's crust. Mountains and... More >>

Sand

Sand is a loose accumulation of tiny pieces of rocks or minerals that are larger than silt or... More >>

Stratified rock

Stratified rock consists of layers, or strata. Strata are also called beds. Each individual layer... More >>

Tektite

Tektite, TEHK tyt, is a rounded, glassy stone that may resemble a ball, disk, rod, button,... More >>