Meet the Latest Sleeper Stone

It's yellowish-green pastel, relatively inexpensive, and it's called prehnite. The last time most of us saw it, we were taking a gem-identification exam. Prehnite is commonly called an ornamental stone, typically described in older gemological texts as, “Seldom seen in jewelry,” or, “Occasionally used as an ornamental object.”

Those old texts may need to be updated. The advent of television shopping, creative marketing, the drive for higher profit margins, and designers' need for unique but inexpensive gem materials has thrust prehnite into the limelight.

A Dutch colonel and South African baron named Hendrick von Prehn (1733–1785) discovered it in South Africa in the 1770s. Mineralogist Abraham Werner (1749–1817) declared the stone a distinct mineral type and named it for Prehn, a good friend of his. It was the first time in history that a mineral was named for the man who discovered it.

In mineral formation, prehnite often occurs in crystalline as well as botryoidal (grapelike bunches) form. It has a somewhat vitreous (glassy) and somewhat pearly luster, which imparts a milky, translucent quality. On rare occasions it occurs as semitransparent.

Prehnite was abundant in Tucson this year, but few took note of it until large quantities showed up at The JCK Show ~ Las Vegas. It ranks at 6 on the Mohs scale. That may seem soft for jewelry, but other soft gems are used extensively, including tanzanite and opal. Prehnite isn't listed in current colored-gemstone pricing guides, which allows more room for profit than most other more popular gems allow.

Prehnite's alleged medicinal/spiritual properties include giving the wearer exceptional vision and reducing high blood pressure. It's also said to be useful for self-hypnosis.