2001 A Gems-From-Space Odyssey

On Dec. 10, 1984, a 3-lb meteorite hit a mailbox in Claxton, Ga. The meteorite—defined as an asteroid fragment that has fallen to earth—was one of many that each year make the long journey from space.

True gem materials can be found in them, but most of these gems are so tiny that when faceted “they would look charming on a bacterium,” says Dr. George Rossman, professor of mineralogy at the California Institute of Technology (Caltech).

But every now and then, a gem large enough to be cut, polished, and mounted up for human adornment comes from space and lands on Planet Earth.

Sudden impact. Some earthly gems result from the impact of a meteorite rather than from the meteorite itself. “We know that a large meteorite that impacts onto Earth or the moon can produce melting of the target rock in the form of melt rock in the crater and splashed materials [e.g., tektites and glass spheres],” says Dr. Harold Connolly, research scientist in the division of geological and planetary sciences at Caltech.

Tektites—specifically moldavite—found in Czechoslovakia originated from a meteorite impact site, the Ries crater, in Germany. “It was blown across to Czechoslovakia,” says Richard Norton, a meteorite expert and author of Rocks From Space. Norton notes that the moldavite is “olive green, with visible flow structures.”

How did a meteorite that hit Germany produce tektites in Czechoslovakia? Norton explains: “The meteor impact threw [pieces of] the earth’s crust up somewhere between 50 to 80 miles into the atmosphere—out of the atmosphere—and then back through the atmosphere. The crust melted, solidified, then melted again when it came back into the atmosphere.” It landed in a strewn field extending from the crater hundreds of miles into Czechoslovakia. The actual “meteorite” material was completely vaporized—with a few exceptions: “Sometimes in the glass you’ll find the metal as droplets,” says Norton.

But an impact does not create gems on or within a meteorite. “When meteorites enter the earth’s atmosphere, only the extreme outer surface [less than 1 mm] is heated and ablates away,” says Connolly. “The inside remains cool, as is observed when fresh falls are found immediately after impact. Consequently, the heating experienced by the outer surface of the meteorite does not affect the inside of the object.”

Star dust. It is said that, wherever you are in the world, if you gaze into a clear and moonless night sky, you’ll see meteoroids as they enter the earth’s atmosphere, burn up, and vaporize in a flash. In scientific parlance, such meteoroids are called “meteors”—what we romantically call “shooting stars.” These momentary streaks of light occur, on average, three or four times per hour.

“Meteor showers,” which occur when a trail of comet dust crosses the earth’s orbit, boost the frequency of shooting stars—and they can be predicted. Here’s the schedule for 2001: Eta Aquarids, May 4; Delta Aquarids, July 27; Perseids, Aug. 12 (about 60 per hour); Orionids, Oct. 21 (about 25 per hour); Taurids, Nov. 2; Leonids, Nov. 17 (“A knockout!” says Norton. “Estimates are running 15,000 per hour in Australia, hundreds here in the States.”); Geminids, Dec. 13 (about 60 per hour).

Catch a falling star. Unless you visit a known meteorite impact site, the chances of finding a small piece of meteorite on the ground are slim, since it has to survive both the atmosphere and the impact. To survive the atmosphere, a meteorite’s original mass must be large. Most earthbound meteorites shatter into hundreds of smaller pieces before they hit, which makes finding remnants even more difficult.

Large impacts are rare, but on Feb. 12, 1947, in Siberia, the Sikhote-Alin meteorite gouged an 85-ft.-diameter crater. Its breakup spawned 122 smaller craters. Over 23 tons of material showered the area.

Of Earth’s 150-plus impact craters, only 16 or so are surrounded by meteorite material. Meteor Crater in Arizona, which measures just under one mile across, is one example. (Some impact sites measure more than 100 miles across.) Scientists theorize that the meteorite that formed Meteor Crater was 100 feet in diameter and shattered before impact. Most of the meteorite pieces have been found within a seven-mile radius of the crater, many in a place called Canyon Diablo.

Jewelry-quality meteorites. There are three main types of meteorites: stony, iron, and stony-iron. Stony meteorites (chondrites and achondrites) are most common, making up 85%-90% of known meteorites. They can be composed of magnetite, serpentine, pyroxenes (related to jadeite), feldspar, and a few other minerals not used in jewelry. Olivine is a major component.

“A stony meteorite is made up of little [millimeter-sized] spherical bodies called chondrules,” notes Norton. “The whole meteorite [typically about 80%] is made up of all these spheres, like little marbles touching each other.” Binding the meteorite together is a fine dust matrix that includes “scattered flakes of iron-nickel that look like little stars.” Norton tells collectors to look for weathering, tiny fractures, and rust in the metal. Non-weathered “stonies” are hard to find, although one notable piece was discovered in Plane View, Texas. It’s also worth noting that “stonies” are the type of meteorite that can contain diamond.

“We really don’t want to see meteorites cut up and used in jewelry,” says Norton. “But there are a lot of meteorite slabs that can be taken and put into jewelry. It isn’t so much the beauty of it that people enjoy, but that the rock you made into jewelry is older than the earth.”

Iron meteorites, composed primarily of 80%-90% iron and 7%-15% nickel, are probably the best known to jewelers. The Meteor Crater and Sikhote-Alin meteorites are classified as iron. Iron meteorites always contain nickel, a combination that doesn’t occur naturally on earth.

Stony-iron meteorites (pallasites, mesosiderites, and lodranites) are the least common, accounting for less than 1% of known meteorites, and arguably the most spectacular. The best gem material, olivines (yes, peridot from outer space!), are found in pallasites. In these meteorites, areas of iron-nickel alloy contrast sharply with portions of gem peridot crystals. “It’s extremely rare to find an olivine crystal that isn’t fractured all the way through,” notes Norton.

The name game. The importance of meteorites in geological studies is enormous. “Yes, meteorites are all named and categorized,” says Connolly. “Several tens of thousands have been cataloged.”

One in particular, the Gibeon meteorite, found in 1836 in Great Nama (“Great Land”), Namibia, is one of the most popular among meteorite jewelry buffs. It’s an iron-type meteorite with an unusual and beautiful octahedral crystalline pattern known as the Widmanstätten pattern, named after its discoverer.

The pattern is a banding of nickel and iron that occurs only in meteors that began as molten cores of asteroids, at temperatures close to 2,500ºF. The material cooled, under near zero-gravity conditions, at an estimated rate of one degree per millionyears. This incredibly slow cooling allows the liquid metal to crystallize. Two alloys, high-nickel taenite and low-nickel kamacite, form during this cooling, crystallizing at slightly different temperatures, and growing into and over each other. The result is the Widmanstätten pattern.

To expose the pattern, the meteorite must be polished, then etched with 10% nitric acid or ferric chloride. The lighter bands are kamacite, and the darker bands are taenite. Scientists have determined that the crystallization of taenite and kamacite in the Gibeon meteorite predates Earth, which puts its origin at more than 4.5 billion years ago.

The Gibeon strewn field is among the largest on earth, 40-70 miles wide and 170-230 miles long. Because of the huge scattered deposit, Gibeon meteorite fragments are fairly abundant. The Sikhote-Alin meteorite strewn field has yielded great numbers of the coarsest octahedrites. And despite the time and care it takes to etch them, meteorite slices are surprisingly inexpensive.

Gemmy gems. There are some exciting finds of transparent gem materials in or around the solar system. The most obvious are the pallasites mentioned above. “You have olivine samples, some which can be centimeter sizes, with the iron rock matrix beneath,” says Rossman, referring to the stony-iron meteorites.

The Imilac meteorite is one of the more important pallasites that contain large, beautiful green olivine crystals. It was discovered in the Atacama Desert of northern Chile in 1822 in a valley southwest of the village of Imilac. The olivine crystals are embedded in an iron-nickel matrix that was probably created during formation of a planet.

“The oldest rocks in the solar system are millimeter- to centimeter-sized meteors known as CAIs [calcium-rich, aluminum-rich inclusions], which are 4.5 billion years old—older than anything else in the solar system, the first solid stuff,” claims Norton. CAIs have diopside and “can also have clear, colorless forsterite (the magnesium end-member of the olivine group), also in millimeter sizes,” says Connolly. “There are clear spinels in CAI meteorites. They’re transparent, colorless to pale-pink to pinkish-purple, but they are very tiny.”

Rossman notes that in the Angra Dos Reis meteorite (not a CAI meteorite), the diopside is a variety called fassaite, occurring as an aggregate of clear, deep-red crystals measuring over a millimeter in size.

Diamonds and moissanite. Space diamonds originate on meteoroids or are created by meteoroid impacts. Gary Huss, senior research scientist in geological sciences at Arizona State University and at the Center for Meteorite Studies in Tempe, Ariz., spends much of his time documenting these space-born gems.

“There are two different kinds of diamond found. [The type found] in achondrites called ureilites, which measure a few hundred microns in size, are apparently created by collision of meteoroid fragmentsfrom asteroids. The others are found in chondrites, also referred to as ‘the ashes of dying stars.’ “

Meteorite dealer Blaine Reed notes that these diamond-bearing chondrites were formed in the outer shell of a dying red giant star. “The explosion of its death then pushed the asteroid out and eventually into our solar system,” he says.

“When a supernova explodes and asteroids fly off, the carbon within the asteroid cools as it leaves the star, creating diamond,” Huss explains. “These diamonds are measured in nanometers, thousands of times smaller than diamond found in urelites, roughly 20,000 atoms in size.”

The Merchason meteorite, a diamond-bearing chondrite, is now being studied to help determine what happened before our solar system formed. In fact, it appears that about 3% of the carbon in the solar system came in as diamond. Huss also notes that moissanite, the natural gem variety, is found in meteorites: “Silicon carbide—moissanite—measuring 0.1 microns up to about 10 micrometers, is another mineral found in meteorites. They look pretty under SEM [Scanning Electron Microscopy].”

“Circumstellar [space-based] Al2 O3 corundum [sapphire] grains less than one micrometer in size exist in some chondrites. We don’t know what color they are, as they are too small [to determine color],” says Rossman. “Microscopic grains of sphalerite exist in one type of chondrite, enstatite chondrite. Again, who knows what their color is—they are simply too small.”

Fly me to the moon. Not all meteorites come from asteroids. “A very few are pieces of the moon [and] Mars,” says Connolly. “We have no evidence at this time that pieces of any other planets are represented in our meteorite collections.”Collecting rocks in space is a continuing goal of the National Aeronautics and Space Administration (NASA). Some rock samples from the moon show clear feldspars and olivines, but mostly small grains. There are also orange and amber glasses present in lunar rocks.

“Clear, pale yellow plagioclase feldspars and pale yellow-green olivines in millimeter sizes occur in the lunar samples from Luna 24, a Russian unmanned mission,” notes Rossman.

Collecting samples from flying asteroids is a different matter. The optical and infrared spectra of several asteroids have been measured, and the data indicate that they are composed of many of the same silicate minerals (e.g., olivine, pyroxene, feldspar, etc.) that we find on Earth.

Martian meteorites contain gem minerals, but in such small grains that it seems of little value to the jewel collector. “To date, the minerals observed within the Martian meteorites are turbid and fractured such that they would not be considered gem quality,” notes Rossman. Connolly confirms that olivine and pyroxenes are found within these meteorites, but that’s all. “If you like the rocks in your back yard,” says Rossman, “then you’d like these.”

Observation vs. ornamentation. “Does science need 10 tons of Gibeon?” asks Norton rhetorically. Those who would slice up a meteorite for jewelry might be attacked by the academic community, but with so much Gibeon around, it seems unlikely that researchers would miss the few hundred pounds that might be used in jewelry. However, some extremely rare meteorites found by dealers and collectors are now being sold, some for up to $2,000 per gram or more—especially lunar and Martian meteorites.

“Should they be bought and sold?” asks Norton. “I don’t care who collects it as long as it is collected and preserved. Otherwise, it will rust away. Get it out of the weathering process. Of course,” adds Norton, “take it to a researcher. Preservation is No. 1 in my book.”

But preservation in a basket pendant might be nice, too.

Special thanks to Drs. George Rossman and Harold Connolly, California Institute of Technology; Gary Huss, Arizona State University; O. Richard Norton, Missoula, Mont.; Blaine Reed, Delta, Colo.; Tim Heitz, “The Midwest Meteorman”; Mike McKnight of the Crystal Ball, Milwaukee, Wis. (www.wehug.com/meteoritegallery.html); and Mama’s Minerals, Albuquerque, N.M. (www.mamasminerals.com).