Hawaii is a well-known source of igneous rock. Most igneous rock forms when hot molten lava cools to a solid state. Metamorphic rock forms when rock undergoes a transformation from one structure to another, usually caused by pressure, heat, and water. For example, a rock that is compacted to a more crystalline condition has undergone a metamorphosis. These resources offer more information about the formation of rock.
Some rock formations develop the unusual property of fluorescence.
The minerals in the rock give off radiation as visible light in certain circumstances. Gemstones possess certain characteristics that make them attractive and valuable. Optical properties and durability are two examples. If a gemstone can be cut such that it reflects light brilliantly it becomes valuable for its luster. Extremely strong gemstones are desired for their durability.