A Gem of a Mineral Collection

What's New in Hillman Hall of Minerals and Gems? Ask Marc Wilson

by Kathryn M. Duda

Marc Wilson has the job he's always wanted: managing one of the premier mineral halls in North America-Hillman Hall of Minerals and Gems at Carnegie Museum of Natural History.

"Pittsburgh has a treasure here," Wilson says of Hillman Hall. "It's a real coup for a city this size. The Carnegie's hall is on a par with mineral halls in cities like New York, Los Angeles, Washington and Houston."

Marc Wilson began at the museum in 1992, twelve years after the opening of Hillman Hall. Under Wilson's stewardship, and with the continued support of The Hillman Foundation, the museum's century-old mineral collection has blossomed as new exhibits are developed and specimens upgraded to include an abundance of world-class minerals and gems. Such continued refinements explain why the hall is a favorite destination among museum visitors.

Chief among the hall's improvements since Wilson's arrival is the complete makeover of the Pennsylvania Minerals exhibit. Obtaining the best available Pennsylvania specimens has long been a goal of the Section of Minerals, and this exhibit represents the roots of the Carnegie's mineral collection. During its first years the museum acquired ores and metals representing Pittsburgh industries-tin, lead, copper, antimony and bismuth. Local steel products, specimens of oil-bearing rock and crude petroleum, and of coal, coke and graphite, were included. Then in 1904, Andrew Carnegie purchased for the museum the mineral collection of William W. Jefferis of West Chester, Pennsylvania. Regarded at the time as one of the finest private collections in the country, the 12,000-specimen Jefferis grouping included a suite of Pennsylvania minerals.

Now, a century later, 90 percent of the Jefferis minerals are in storage to make way for the new specimens that are on long-term loan from the private collection of Harrisburg resident Bryon Brookmyer, whom Wilson describes as "one of the top collectors of Pennsylvania minerals." The new exhibit contains more specimens than the previous exhibit did, and the minerals are of a higher quality.

"Visitors have a great opportunity to see some of the finest Pennsylvania minerals," says Wilson. "The mining that produced many of these specimens ended about 100 years ago, and most people will never see even one example of minerals like these. Yet we have all of it here together in one spot. It's outstanding."

Adults enjoy the hall, but Wilson wants children to be impressed as well. The father of a six-year-old, Wilson knows that to interest a child, he needs an exhibit that allows hands-on investigation. The result is a display of "float" copper, which consists largely of a 2,200-pound chunk of copper showing both a smooth, polished section and the rough natural surface of the rock.

As glaciers moved along Michigan's Keweenaw Peninsula 70,000 years ago, they tore copper from billion-year-old copper-bearing basaltic rocks and carried it along, finally depositing it in glacial outwash. It is referred to as "float copper" because early scientists thought that the copper floated in glaciers.

The gemstones section includes a new addition-amber. Beautiful as well as educational, the exhibit shows the two types of amber-succinite, formed from fossilized evergreen trees; and retinite, from fossilized leguminous trees. We also see two types of a common amber substitute, copal, which is a product of modern leguminous and coniferous trees. Amber and copal are shown in their rough forms, and as freeform polished specimens and jewelry. Insects embedded in amber demonstrate how life forms become fossilized in the resin.

"By the strict definition, amber is not a mineral, because it is organic, with no set composition and no crystal structure," Wilson says. "But it is considered a 'mineral substance' in most treatments of minerals because it is naturally occurring and because it is like a rock in the same way that coal is considered a rock, even though coal is organic."

The continuously evolving nature of the hall was evident in late October 1996, when Wilson unveiled a new exhibit of Pseudomorphism in Minerals. A pseudomorph is a mineral that takes the shape of another mineral. How can that be? The transmogrification is caused by changing conditions in the crystal's environment. One example is the museum's first world-class mineral specimen, accessioned in 1897-a pseudomorph of hemimorphite after calcite. This pseudomorph was originally calcite, but hemimorphite grew over the calcite crystals. In time the calcite crystals inside were removed naturally through a chemical change, leaving a shell of hemimorphite. As the calcite was removed, hemimorphite also grew inside the cast. Wilson explains the process:

"Calcite is a carbonate that is very susceptible to acid. There was probably carbonic acid in the groundwater, as well as sulfuric acid generated from the oxidation of sulfide ore minerals in the rocks, which etched away the calcite as the hemomorphite was deposited."

In nearly 100 years the museum's pseudomorph of hemimorphite after calcite has not been surpassed, and it remains perhaps the most significant specimen in the collection.

"Only about six pieces of this specific type are known," says Wilson, "and I think they all came from the same pocket, in Joplin, Missouri. This is by far the largest."

Like the amber and float copper exhibits, the new pseudomorph exhibit contains more educational text than earlier exhibits in Hillman Hall-another sign of Wilson's interest in educating his audience.

Because he wants to impart more information than can fit on text panels in the exhibits, Wilson plans to add a computer station in the hall to give visitors access to complete information on any specimen on exhibit. To his knowledge, no other museum offers a computer station with such a comprehensive database.

Scheduled to open in mid-January 1997 is the Minerals of the Former Soviet Union exhibit-some 30 spectacular minerals from the recently acquired collection of 250 high-quality specimens. Minerals from the former Soviet Union have only recently begun entering western collections as a result of the fall of communism several years ago.

"With the overthrow of the czars and the institution of the communist regime in 1917, some of the most significant mineral deposits on Earth went behind the Iron Curtain," says Wilson. "For a very long time nobody in the west knew what minerals were being found there."

Western mineralogists did know, however, that the mines were producing phenomenal specimens, for the Soviet Union had the largest mining industry in the world.

"Along that huge land mass is Precambrian rock, which is especially likely to host a wide range of high-grade mineral deposits," says Wilson. "Plus, in a communist regime, the mines didn't have to make money. They could be subsidized and would operate as long as they were producing. Now, in a freer market, those mines are closing."

With the fall of communism and the rise of capitalism came freedom for Soviet collectors to show their treasures and to sell them.

"When the communists were in control, collectors risked Siberia or worse for amassing minerals-which represented material wealth and stealing from the state," Wilson explains. "But when things loosened up, it became acceptable for citizens to admit that they had specimens."

The Soviet minerals, seen for the first time by the modern western world, soon redefined quality for many species. Western buyers immediately contacted the Soviets and purchased some of the most significant mineral specimens in the world. Carnegie Museum of Natural History acquired an amazing collection for Hillman Hall.

Also on the drawing board is a permanent birthstone exhibit. Visitors may remember a temporary birthstone exhibit in Hillman Hall several years ago, an exhibit with some specimens that did not meet the quality standards required for permanent display. New gemstones have been acquired for the proposed birthstone exhibit, but four cut stones are still needed-a large emerald, two rubies of different shades of red and a sapphire. "It's going to cost about $200,000 to get those four stones," Wilson sighs. "We've looked and priced them, and are keeping in contact with collectors who have what we're looking for." New minerals for the hall are bought at gem and mineral shows held around the world, and from private collectors who Wilson visits personally.

"We go to five shows a year," Wilson says, "and there's potential at each of them to come back with specimens." Most of Hillman Hall's exceptional specimens come from the Tucson Gem and Mineral Show, the largest and most important show of its kind. Wilson responds to calls from collectors around the world who "think they have specimens we can't live without." He looks into those offers with the help of an international network of fellow mineralogists.

"I follow up on all calls, but usually minerals from outside the U.S. are not as important to us, because the [non-U.S.] philosophy of what constitutes a good specimen differs from ours, even among professionals," Wilson explains. "In Europe, damaged specimens are acceptable, but in Hillman Hall they are not."

While most acquisitions are made on the basis of sheer beauty, Wilson collects gems and minerals for Hillman Hall in three categories: masterpiece specimens-the large, unique, aesthetic pieces that cause visitors to gasp in amazement; systematic specimens-top-quality examples of as wide a range as possible; and reference and research pieces needed to fill in gaps in species, to create suites from specific important localities and to keep for future study.

"Consistent support from The Hillman Foundation and the Hillman family has given us an active acquisition program that is the envy of many institutions," Wilson says. The hall impresses collectors and professionals from around the world. Some mineralogists and exhibit professionals visit to gather ideas for building their own new mineral halls.

In addition to attracting individuals and school tours, Hillman Hall reaches out to the world in several ways. Wilson speaks regularly to mineralogical clubs and societies locally and nationally, and research associate Donald Palmieri teaches popular gem classes at the School of the Carnegie. Also, the museum annually presents the Carnegie Mineralogical Award, an internationally renowned prize that honors outstanding contributions in mineralogical preservation, conservation and education that match ideals advanced in Hillman Hall. Consisting of a bronze medallion, a certificate of recognition and a check for $2,500, the award is presented at the Tuscon Gem and Mineral Show. Past winners include Marie Huizing, managing editor of Rocks & Minerals magazine (1995); the Mineralogical Record magazine (1994); Cornelius Searle Hurlbut III (1993): Carl A. Francis (1992); Miguel A. Romero Sanches (1991); the late Paul E. Desautels (1990); Frederick H. Pough (1989); John Sinkankas (1988); and the Tucson Gem & Mineral Society (1987). The Carnegie Mineralogical Award is underwritten annually by The Hillman Foundation, Inc.

Wilson is also recataloging all 21,000 specimens in the collection. "It's a tremendous job, and I don't think it has been done thoroughly since the museum opened a century ago," Wilson says. Over the years, specimens have "died" through oxidation or dehydration. How can a mineral die? To explain, Wilson reaches under his desk into the wastebasket and pulls out a crumbly grey rock-a dead mineral. It's marcasite, an iron sulfide, which is obvious by the smell.

"Marcasite absorbs water from the atmosphere, and as it oxidizes it creates sulfuric acid, which attacks the rock that the crystals are growing on as the crystals themselves decrepitate," Wilson says. Other minerals can dehydrate, such as laumontite-a zeolite mineral containing a large amount of water.

"When that happens, they just turn into a pile of dust. Pyrite and marcasite are even susceptible to a bacteria. They can catch a disease called pyritis, which accelerates the oxidation process." It is difficult to know when this will happen to a mineral when one makes a purchase, for according to Wilson, there is no normal lifespan for a mineral. "Two specimens of the same mineral can have lifespans as different as one year versus 50 years," he says.

For Wilson, no subject is too elementary to discuss, and no task too menial when it comes to mineralogy. He is passionate about his work, and about Hillman Hall. A geologist and mineralogist, his energies have been focused on things below ground since childhood.

"When I was four years old, I came out of a field next to our house in Southgate, Michigan, clutching a little plastic dinosaur. From that time on I knew I was going to be a geologist." In junior high school Wilson changed his focus from paleontology to mineralogy, and from there he geared his education in that direction.

"In college I studied geology so I could be close to minerals, and when I got my masters I concentrated on mineralogy." Jobs in his chosen field are difficult to come by, but Wilson has spent his entire career as a geologist, first working for two mining companies in hard-rock mineral exploration, and then for a remote-sensing consulting firm. Most recently he was curator of the New Mexico Bureau of Mines Mineral Museum and "essentially the state mineralogist."

Mineralogy is a family affair in Wilson's home. His six-year-old son, Cedric (named after the son of a Parisian mineralogist friend), already has his own rock collection and models of all the Carnegie dinosaurs.

"While we let him choose his own interests and try to encourage him in any way he wants to go," Wilson says of Cedric, "he says he wants to work in a museum with rocks and dinosaurs when he grows up." Wilson's wife, Debra, has a notable collection of thumbnail minerals-specimens that fit in one-inch cubes. A professional photographer, she has captured on film many of the Carnegie minerals. Aside from their shared interest in mineralogy, Wilson and his wife have been active in their church-he in the Sunday School program, and she in the music ministry. Wilson finds a certain spirituality in his profession, as well. Being surrounded by many of the finest mineral specimens available is to him as close to heaven as a mineralogist can get.

"Crystals to me represent a microcosm of the order of God's creation," Wilson says. "They are so perfect, so ordered, so beautiful. Each one is unique, and the best are of a beauty that is not matched by anything humans try."

Kathryn M. Duda is associate editor of Carnegie Magazine.