It's the latest trend in makeup, and yet its ingredients are as old as the hills.

Minerals are popping up in foundations, lipsticks and eye shadows. They're said to soothe acne. They're supposed to slap down sun rays that damage skin.

They're getting so much good press, you'd think they could also throw a dinner party for 12.

"We're really happy the craze of mineral makeup is here," said Staci Wilson, vice president of brand awareness for Bare Escentuals, a makeup line that has incorporated minerals since 1976. "For years, it was hard to get people to comprehend what we offered."

The line is now sold at Sephora and on QVC, a home-shopping network.

Competition in the mineral-makeup industry has soared recently.

Spas and salons in particular all seem to carry their own lines of mineral makeup. That's because trade shows are chock full of mineral-makeup manufacturers that can put any label on generic containers of powdery rose blush.

A few of the major beauty companies have jumped on the mineral bandwagon, including Neutrogena, with its Mineral Sheers foundations and eye shadows.

Peruse major makeup counters, however, and you'll find few products advertised as mineral makeup. Among Estee Lauder brands, only Aveda and Origins have lines that promote rock-derived ingredients.

But that doesn't mean other cosmetics don't have minerals in them, said Harvey Gedeon, head of research and development for Estee Lauder brands. Zinc oxide, for instance, is commonly added because it adds sunblock, and iron oxide is a colorant. But marketing for such products doesn't always play up those ingredients.

"It's more about positioning to me, than technical," Gedeon said.

The buzz about mineral makeup is that it's actually good for the skin.

Paula Begoun, who studies thousands of products a year and criticizes many of them in her books, including "Don't Go To The Cosmetics Counter Without Me" (Beginning Press, $27.95), now in its sixth edition, isn't impressed.

"Minerals are drying, and not all (skin) types can use them," said Begoun, whose Web site is CosmeticsCop.com. They are messy, and can look powdery and thick, she said. "I don't see it as quite the slam dunk as it's advertised."

Zinc is thought to be an anti-inflammatory. And minerals in general are said to cause less interference with normal skin processes because they sit atop the skin, rather than get absorbed the way regular makeup does.

Said Robin McGee, vice president of business development for Caleel + Hayden, manufacturer of GloMinerals, a line launched in 2002: "Your natural oils and waters continue to flow naturally, whereas other makeup suffocates the skin."

Since the makeup industry is unregulated, there are few if any independent medical studies addressing claims that mineral makeup is beneficial to the skin. Companies say they do their own studies, but those are rarely released.

Minerals don't come in a rainbow of colors.

Rose and violet shades _ not to mention electric blue _ give chemists heartburn. So many mineral companies add dyes to some products, and that's not necessarily a bad thing, said McGee, who is based in Denver.

"For 100 percent pure minerals without any artificial colors, you might have a line that sacrifices color and wearability," she said.

Loose powders are the purest form of mineral makeup. Compresses require some binding agents. And liquids have more additives.

But not all minerals are created equal, according to purists. Talc is often vilified by those who say it accentuates wrinkles. But if this is an argument you buy, you'll have to dump many of your cosmetics; it's a common component in makeup, from Maybelline to Chanel.

Gedeon thinks talc is getting a bad rap.

"Talc is used because it's very transparent and tactile and soft. It's a natural ingredient. There's absolutely nothing wrong with talc."

Begoun echoes that defense: "I have seen no evidence that a well-formulated talc powder makes wrinkles look worse."

Minerals used in cosmetics are all the same grade.

The difference, say industry insiders, lies in the milling process. The more that minerals are ground, the finer and silkier they become, appearing less shiny on the skin.

A gritty feel means the minerals haven't been milled into small enough particles.

"You can literally put a bunch of mineral makeups in front of you and feel the texture of one being more gritty or silky," said Staci Wilson, of Bare Escentuals.