Marilyn Monroe, who famously said, "Diamonds are a girl's best friend," probably hadn't heard of Sardinian ichnusaite.
Or maybe go with cobaltomenite, a pink-red mineral found in just four locations -- Utah, Argentina, Bolivia and Congo.
As the Los Angeles Times reports, cobaltomenite is so rare that the Earth's supply could fit in a shot glass.
In a study to be published in American Mineralogist, Hazen, of the Carnegie Institution in Washington, and Jesse Ausubel, a scientist at The Rockefeller University, inventoried and categorized more than 2,500 minerals -- the rarest of the rare. Each comes from five or fewer known sites worldwide, and several have a known supply smaller than a sugar cube.
"These 2,550 minerals are far more rare than pricey diamonds and gems usually presented as tokens of love," the authors wrote in a statement.
But there's one major problem for those thinking of putting the rare minerals on a wedding band.
"Several are prone to melt, evaporate or dehydrate," the authors said. "And a few, vampire-like, gradually decompose on exposure to sunlight."
While there are more than 5,000 confirmed minerals on Earth, fewer than 100 of them make up 99 percent of Earth’s crust, according to the study.
It's the rarest ones, Hazen told BBC News, that make Earth special and are "key to the diversity of the Earth's near-surface environments."
In their paper, "On the Nature and Significance of Rarity in Mineralogy," Hazen and Ausubel categorize rare minerals based on the unique conditions that created them, the rarity of their ingredients, how ephemeral, or short-lived, they are, and the extreme, remote locations where they are found.
"It's made of rare elements -- vanadium and copper have to exist together, and it forms under an extremely narrow range of conditions," Hazen told BBC News. "If you just change the ratio of copper to vanadium slightly, you get a different mineral. And every time it rains, fingerite washes away."
So, basically, if you're hoping for a dark-red hunk of cobaltomenite or a piece of nevadaite next Valentine's Day, keep dreaming.
Also on HuffPost: