Although most of us are familiar with meteorites as interesting collector items, far fewer realize that they, along with some related specimens, can be beautiful additions to a gem or jewlery collection. The majority of the essay that follows was written by one of my colleagues at CSN, Dr. David Batchelor, a specialist in planetary geology. In Astronomy 103: The Solar System, one of the courses David teaches (in person and online through CSN's Distance Education Department), the topic is developed in greater detail.
Most meteorites are pieces of asteroids, which are leftover building blocks of the planets. The more common meteorite types are chemically and geologically primitive, and while their chemistry may offer a fascinating glimpse into the planet-forming process, they are both too fragile and too drab to be of gemological interest (most look like ordinary dull grey rocks). Nevertheless, there are some meteorites and related materials suitable for jewelry.
Irons: A handful of asteroids grew large enough to differentiate; they had enough gravity to pull theiriron content away from the rock and down into a core. Iron meteorites, which are really alloys of iron, nickel, and other metals, are fragments of these cores.
Their fascination as jewelry comes primarily from their Widmanstätten patterns, which are seen only after a piece is cut, polished, and etched with 2% nitric acid in alcohol. At the concentrations found in these meteorites, iron and nickel do not mix, but separate into two types of crystals; plates of the low-nickel alloy kamacite grow in octahedral shapes, with the high-nickel taenite alloy filling in the spaces. Specimens from deeper within the parent asteroid have cooled more slowly, and their crystals grew larger. Much of the gemological skill in fashioning these pieces comes from selecting a piece with appropriate crystal size, cutting it to display the pattern to advantage, polishing and etching it to bring out the pattern, and somehow protecting it from rust.
Pallasites: The most beautiful of all the meteorites, the 50 or so Pallasites are iron meteorites with silicate rock inclusions, often of amber to pale-green olivine crystals, gemologically known as peridots. The Pallasites all come from the core/mantle boundaries of three different parent asteroids, and are collectively named after Peter Simon Pallas, who described the first known example, found near Krasnoyarsk in Siberia. They can have intact olivine crystals large enough for jewelry use.These specimens are often sliced to give a stained-glass effect, or individual peridots are faceted.
Tektites: When meteorites hit the surface at high speeds, the target rock, soil or sand is melted, and droplets solidify into glassy tektites. They occur in four particular areas on Earth, three of which are centered around known impact craters.
(The number of named tektite strewnfields has actually shrunk over the years, as what were previously believed to be separate field were found to be parts of larger fields spreading across multiple continents. The Bediasites from Texas and the Georgiaites from Georgia are now recognized as part of the North American strewnfield from the 34 million year old Chesapeake Bay crater. The Australites, Chinites, and Indochinites are now part of the Australasian strewnfield, for which no crater has been found despite a relatively young age of 600,000 years. And 1 MY old tektites from Africa and Australia are part of the Ivory Coast strewnfield associated with a crater at Lake Boumtwi in Ghana.)
Although there is significant evidence they formed from craters on Earth, a handful of prominent researchers cite contradictory evidence and argue for an origin from craters on the Moon. Some of the prettiest tektites are from the strewnfield along Europe's Moldau river, associated with the 15 million year old Ries Crater in Germany. These "Moldavites" are a striking green, with surfaces apparently shaped by wind as they descended through Earth's atmosphere.
Impactites: One of the most mysterious materials in this general group is called Libyan Desert Glass. Found in remote areas of the Sahara often in quite large pieces, Technically, the Libyan Desert Impact Glass samples aren't tektites, although they are also bits of glass formed by meteorite impact. Tektites specifically show aerodynamic shapes from reentry through the Earth's atmosphere. (Or entry, if you allow for the possibility of a lunar origin.) The more general term "impactites" includes tektites, melt glass, impact breccias, shattercones, or any bit of geologic evidence of impact.
This is a bit of a stretch, but kind of fun. In 1893 a French scientist Henri Moissan began studying fragments of meteorites from Arizona's Meteor Crater. Dr. Moissan discovered microscopic crystals of quantities of a new mineral, today known as a form of silicon carbide. In 1905, this mineral was named Moissanite, in his honor. Although opaque, non-gem forms of silicon carbide could be found and/or manufactured and were used extensively as industial and lapidary abrasives (harness = 9.5), none of the transparent, single crystal gem type was made until 1995. Recently Charles and Covard Company has patented the production process and is offering the near colorless form of the gem as a diamond simulant.
As huge crystals are available, the value of gems or carvings from this material is almost entirely due to the beauty, interest or artistry of the piece.