Jewels and jewelry have constituted kings’ ransoms and motivated murderous coups.

In peacetime, they’re desirable as investable assets, but more for beauty than intrinsic value.

“[We] always recommend clients buy jewelry to wear and enjoy, rather than specifically for investment purposes,” says Jean Ghika, director of jewelry at Bonhams in the UK and Europe. “However, some clients are attracted by the fact that jewelry is a tangible asset that may grow in value.”

For that reason, National Gemstone, a U.S.-based dealer, suggests investors place no more than 15% of a portfolio in jewels and spend at least $10,000 on one or two high-quality gems.

At Bonhams, fine jewelry pieces sell for at least £5,000 ($7,754). In September 2011, the auction house sold a Bulgari diamond and blue diamond crossover ring for £1.9 million. So there are multiple entry points for new and seasoned buyers.

Several factors make jewelry and gemstone investing sound. There aren’t many pieces outside of private collections, and the stones are a finite resource. Plus, the global economic situation is making gems more attractive. Clients are putting their money into tangible assets at a time when bank accounts yield very little interest. In uncertain economic times, owning jewelry is comforting because people can see and feel their investments.

What to buy

“Signed pieces from the best jewelry houses—Cartier, Van Cleef & Arpels, Boucheron—rarely lose their value and often appreciate over time,” says Ghika. There is also strong demand for art-deco jewelry. A Cartier art-deco diamond necklace sold at a Bonhams auction in 2010 for £264,000.

Natural pearls are another sound investment, commanding prices often ten times over the presale estimate. That’s because they take years for oysters to produce, and compiling a strand matched for colour, size, skins and lustre can take decades.

And then there is the king of gemstones: the diamond. Commercially promoted as a girl’s best friend, diamonds are one of the best-known and most sought-after rocks.

For diamond jewelry, Ghika recommends buyers use a “loupe magnification device to examine a piece for any marks, solder work or repair, and to check there are no stones missing.” It’s best to consult expert appraisers.

Any loose diamonds should be certified for clarity and colour. “Steer clear of anything that’s not certified from a reputable laboratory,” she says. “It’s better to buy a smaller stone that’s better quality rather than a larger stone of lesser quality.”

The same holds true for coloured stones. Some of the most desirable coloured stones in the marketplace are the rare ones: Kashmiri sapphires, Columbian emeralds and Burmese rubies.