Chemical Compounds That Incite Oohs and Aahs

Jewelry and art have long captivated both collectors and the general public, but recently, fine minerals — topaz, quartz, calcite and more — have also been figuring in.

Case in point: The multidisciplinary art fair Masterpiece London, set for June 30 to July 6 at the Royal Hospital Chelsea, will have a new exhibit by the New York-based Fine Minerals International, which sells, buys and mines rare minerals. It will be the first time that the more-than-decade-old fair will showcase minerals in a dedicated display. Sixty of these rare objects will be on view, including an amethyst from the Goboboseb Mountains in Namibia, a rhodochrosite from Colorado and a tourmaline cluster from Brazil.

The founder of Fine Minerals International, Daniel Trinchillo, said he began collecting the stones when he was 8 years old. “I found a garnet in our neighbor’s front landscaping and was so struck by how beautiful it was,” he said. “My lifelong pursuit of fine minerals started at that moment.”

Mr. Trinchillo described a mineral as a naturally formed chemical compound with a crystal-like shape. He said the five most sought-after varieties included tourmaline, aquamarine, crystallized gold, fluorite and rhodochrosite.

The exhibit at Masterpiece London coincides with a time when interest in fine minerals is growing.

Christie’s, for example, now has two annual online auctions dedicated to fossils, meteorites and fine minerals, according to James Hyslop, its head of science and natural history, who oversees these sales. When Christie’s began selling the objects in 2011, they were available once a year in various auctions. Back then, the total sales volume was $500,000, but in the most recent auction, which concluded at the end of May, that number was closer to $15 million.

The American Museum of Natural History also opened a redesigned 11,000-square-foot space for gems and minerals last June. Called the Allison and Roberto Mignone Halls of Gems and Minerals, it has more than 5,000 fine minerals on display and is one of the museum’s most visited areas, according to a spokesman, Scott Rohan.

In a recent interview from Idar-Oberstein, Germany, a global center for stones and gems, Mr. Trinchillo spoke more about fine minerals and their budding popularity. These are edited excerpts from the conversation.

Why is now the right time to bring fine minerals to Masterpiece London?

Minerals have been escalating significantly in interest and value over the last decade. The first time I sold a mineral for $1 million was in 1999, but now it happens regularly.

Historically, collectors stemmed from science backgrounds, and they valued minerals for both their complex chemical structures and colorful crystallization. Now, they value the beauty and aesthetics over the composition and consider a mineral’s luster, transparency, crystal form and geometry.

How and why has interest in collecting them grown?

Fine Minerals International is now selling $25 to $50 million a year in minerals, compared with a decade ago, when we had half that number — and we are just one dealer out of thousands. Collectors are seeking items in categories that aren’t so saturated, and minerals offer that. The price point of entry is also reasonable: You can build an entry-level minerals collection for a few thousand dollars.

What makes some minerals so rare, and how is their value determined?

Rare minerals are ones that have a complicated chemical structure. They also have certain characteristics, including quality of the crystals, translucency and the color — stones that are richly colored typically have more value.

Luster is also important: If the surface is glassy and has a mirror-like quality, it’s more desirable. Then there’s form — the more geometric a stone, the more valuable. A stone that resembles a blob isn’t as valuable.

Crystals that are more clearly defined and not grown together in a jumble — this quality is called crystal isolation — also get more money.

How are minerals sourced?

There are certain countries that produce more minerals than others — China, Brazil, Pakistan and many countries in Africa including Mozambique, Tanzania, Congo, Zambia and Madagascar. In the United States, you can find them in Arizona and in San Diego County, where there are tons of gem mines.

But you don’t have to go far from home to find minerals. There are quarries all over the country where you can find calcite, quartz and pyrite. It’s a superfun activity to spend an afternoon mining, and you pay a dig fee to do so. Herkimer Diamond KOA Resort, which is a few hours from New York, is one of my favorite ways to spend a day with my kids.

What is the size range of fine minerals, and are the larger ones more valuable?

There is no direct correlation between size and value. The most popular size and the sweet spot for most collectors ranges from an orange to a small cantaloupe. You can also find them in micro sizes — such as the size of your thumbnail — or as big as 200 pounds.

What about pricing? What is the point of entry and the upper limit?

One million dollars is now common for top-quality minerals, but they do go for as high as $40 million.

What are some standout stones from the exhibition, and what characteristics make them exceptional?

We’re displaying a blue cap tourmaline that was found in 1972 in a San Diego County mine. It’s about the size of a soda can and over half a billion years old. The crystals are large and so sharp that they look like they’ve been cut by a machine. They have a rich red hue and are capped by a sapphire blue.

Stibnite from Hunan province in China is another highlight. It’s a basketball-sized metallic mineral with sulfur and antimony and looks like a burst of crystal. Its three-dimensional quality is exceptional. It’s probably worth around $125,000.

My third pick is a crystallized gold from a mine near Sacramento, Calif. The luster is super shiny and brilliant. It’s worth close to $500,000.

What advice do you have for buyers who are new to collecting fine minerals, or who are interested in doing so?

Before buying anything, familiarize yourself with minerals as much as you can — seeing them is the best way, so it’s worth going to a minerals show or gallery. You can also browse a site like mindat.org, which tells you about different species of minerals globally, or even peruse eBay.

The more you know, the more you can figure out what appeals to you and where you want to put your money.

My other tip would be to buy what you love and not because you think it’s a good investment. Minerals are beautiful objects that are meant to be admired. As their owner, you need to appreciate them, first and foremost.