Glass in Nature
Glass Collection Galleries
The Museum’s Glass in Nature display features a range of glasses that are found in—and formed by—nature.
Watch Glass in Nature presentation
Although most people think of glass as a man-made material, it is found in many forms in the natural world. Volcanoes spew molten rock, lightning strikes desert and beach sands, meteorites pound the earth, and sea sponges and microscopic organisms inhabit the waters. All of these things—and even lunar soils—are related to the man-made glass that we use every day. How is this possible?
Scientists tell us that glass is a state of matter rather than a single material. Glass is formed when a molten material cools so rapidly that there is not enough time for a crystalline structure to form. To the scientist, crystals are materials that have their atoms arranged in perfectly-ordered, lattice-like structures. Think of them as three-dimensional checker boards or three-dimensional wallpaper in which every atom is located exactly where it belongs in a perfectly-ordered state. In liquids, atoms and molecules are free to move about in a random way—which is why liquids can flow. In a glass, the atoms are held rigidly in place so it can not flow. But they have not had time to arrange themselves in the perfectly-ordered lattice that nature would have liked. Neither a solid nor a liquid, glass is often called a rigid liquid.
Obsidian or volcanic glass, for example, is molten rock that has quickly cooled, becoming rock in a glassy state, just as boiled hard sugar candies are sugar in a glassy state. In nature, glasses are formed when sand and/or rocks, often high in silica, are heated to high temperatures and then cooled rapidly. Glassy materials share certain characteristics, such as shiny surfaces, brittleness, and the tendency to form conchoidal (shell-like) fractures. They do not show the regular, geometric x-ray diffraction patterns characteristic of crystalline solids.
Sea sponges and microscopic organisms are life forms that contain silica, the main ingredient of man-made glasses. Glass sponges, which live in the deep ocean, have skeletons made of silica spicules. These spicules are made from dissolved silica that they ingest from seawater. They transmit light in a manner similar to that of the glass optical fibers used in telecommunications.
“Glass in Nature” is drawn from the Museum’s permanent collection. It includes a variety of tektites, most of which were collected in southeast Asia and China. These tektites were created by the intense heat and force of meteoritic impacts on the earth millions of years ago. Libyan desert glass, almost pure silica, is represented by an unusually large specimen from the Great Sand Sea, which spreads across the border of Libya and Egypt. The large silica glass field there is believed to have resulted either from a meteoritic impact or from a comet exploding in the earth’s atmosphere.
The exhibit also features glass made by lightning, or fulgurites. Sometimes called petrified lightning, fulgurites are found everywhere. They are formed when lightning strikes sand. This happens naturally, but fulgurites can also be intentionally made by attracting lightning to sand. These hollow tubes vary in length from a few inches to several feet, and they break easily.
Marine Diatoms - 50 Species, by Randolph Femmer. Photo courtesy Randolph Femmer/NBII.Gov.
Marine creatures with siliceous (silica) skeletons, such as certain varieties of sea sponges and microscopic organisms, are also found in the Museum’s collection. Organisms, such as radiolarians (protozoans) and diatoms (algae), are represented in the display by photographs and by reproductions of 19th-century illustrations made by Ernst Haeckel, the German naturalist and philosopher.
One type of glass in the Museum’s display is not made in nature, but it is man-made. This is Trinitite, which was collected at the Trinity test site of what is now the White Sands Missile Range in White Sands, New Mexico. Trinitite was unintentionally created by the United States Army on July 16, 1945, during the testing of the Trinity atomic bomb. However, the way in which this glass was created mimics how glass is naturally formed by meteoritic impacts and by lightning strikes.