Native Element Graphite

Associated Smithsonian Expert: Jeffrey E. Post, Ph.D.

Jeffrey Post

Photograph by Cara Santelli, Smithsonian Institution

Dr. Jeffrey Post is the curator of the National Gem and Mineral Collection at the Smithsonian National Museum of Natural History. As far back as he can remember in childhood, Post collected rocks and fossils around his home near Madison, Wis. The symmetry of mineral crystals fascinated him, and experiments with a large chemistry set helped develop his interest in science. He earned a Ph.D. from Arizona State University in 1981 and joined the Smithsonian in 1984. Post’s research projects include the physical and chemical properties of fine-grained, environmentally significant minerals such as clays, manganese oxides, and iron oxides. He also uses powerful X-ray beams at the National Synchrotron Light Source at Brookhaven National Laboratory (Upton, N.Y.) to study the crystal structures of these minerals. With his Smithsonian colleagues, Post is always seeking new gem and mineral acquisitions for the Smithsonian. He analyzes specimens to resolve curatorial questions, oversees loans of Smithsonian gems to other museums, supervises the team that is building the collection website, meets with donors, and answers public inquiries about the Smithsonian mineral collection.

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This image was obtained from the Smithsonian Institution. The image or its contents may be protected by international copyright laws.

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Native sulfur, Italy
Photographed by Ken Larsen, Smithsonian Institution

What Are Native Elements?

In nature, only a few elements occur in their native form as a single, solid element, not chemically combined with others. Gold, the best known example, is less chemically active than most other elements that exist in solid form. Gold occurs as tiny particles in rocks; as hot water seeps through bedrock, it may carry the gold bits until they accumulate into small nuggets. A few other metals, such as silver and copper, are sometimes found in small standalone amounts in nature. Whether silver, copper, and platinum combine with other elements or remain as native elements depends on their proximity to other chemically active substances. A few nonmetallic elements also may occur in native form. For example, plain sulfur collects around the vents of hot springs and volcanoes, as well as in sedimentary structures like salt domes. In nature, carbon can appear in two different native forms, graphite and diamond, depending on how much heat and pressure have been applied to it.

Diamond is one of the polymorphs of carbon
Photo by Smithsonian Institution, National Museum of Natural History, Department of Mineral Sciences

Polymorphic Minerals

Polymorphic minerals have the same chemical composition but different crystal structures. (The word "polymorphic" means "many forms" in Greek.) These structures may have vastly different properties. Polymorphism occurs because the minerals crystallized under different temperature and pressure conditions. The most well-known example of polymorphism is carbon: it occurs both as graphite - a soft, opaque mineral that splits into layers - and diamond - transparent and the hardest substance on Earth. Silicon dioxide has several polymorphs: quartz, tridymite, cristobalite, coesite, stishovite, and seifertite. The last three of these polymorphs form only under extreme conditions of temperature and pressure - in meteorite impacts in nature or experiments in the laboratory.

Modern copper cable
Photo by Giovanni Dall'Orto (WikiCommons)

Minerals in Electrical Technology

About 200 years ago, scientists studying electricity realized that metals allowed electrical currents to flow through them much more easily than most nonmetals. Because of its relative abundance, high electrical conductivity, and malleability (or ability to be shaped), copper has become the standard material for electrical wiring and switching. Certain types of low-iron silicates, such as muscovite and pyrophyllite, are naturally occurring electrical insulators. Glass or porcelain insulators, made from such minerals as quartz and feldspar, keep high-voltage power-transmission lines from touching their poles. Pyrolusite is the naturally occurring mineral version of manganese oxide, which is inside every non-rechargeable alkaline battery. Gasoline-powered articles start their engines with a jolt of electricity from lead-acid batteries, which get their lead from the mineral galena. Other rechargeable batteries contain nickel, cadmium, or other metals, found in a variety of ores.