Brenda Buck, a UNLV geoscience professor, holds an average piece of landscaping rock that contains pyrite, also known as fool's gold. Once the rock comes into contact with water, Buck's research shows, an acidic reaction will produce a salt crust with concentrated levels of heavy metals that can leach into the environment. Photos by Jane Kalinowsky. Brenda Buck shows a nugget of the green salt covering that develops on sulfide-bearing rocks. Because copper sulfate concentrated in the salt can irritate or burn skin on contact, she wears gloves when handling the salt.

Those pretty pink rocks you use to decorate your front yard may seem so innocuous, so inert.

But Brenda Buck, a UNLV geoscience professor, has found that some boulders and ground covers aren't so friendly.

Her research, which will be published in an international journal this fall, has found that newly placed sulfide-bearing rocks react to water and leach heavy metals and copper sulfate into a concentrated salt crust that can damage the surrounding environment.

"I would tell my child not to walk on it, don't touch it and, if it's a windy day and it's out there on the playground, stay inside," she said of the crust. "I wouldn't freak out about it."

The problem in the granite rocks she studied from local public sites is pyrite. The sulfide, also known as fool's gold, occurs naturally in all kinds of rock and can be invisible to the naked eye. But it has an acidic reaction to water that sets the inert metals inside the rock, such as lead, arsenic and zinc, free to flow with water and evaporate into green, yellow or blue salts.

Nevada's soil acts as a base and prevents the metals from entering washes and Lake Mead, Buck said. After a period of time, depending on the size of the rock, the reaction is neutralized as water continuously dissolves the salts and the crusts disappear.

Her report does not include an analysis to determine the effect on human or environmental health.

Buck's main concern is banning tainted rocks in Nevada. A geologist should inspect rocks before they're removed from quarries.

"It's just like e-coli and meat. You need an inspector to check the meat," she said.

The copper sulfate found in the salt can irritate or burn the skin. Nearby plants ingest the heavy metals, causing them to get sick or die. The salt can even destroy nearby infrastructure, she said.

"This is such an easily prevented thing. If we just added regulations we'd never truck it in," she said.

Sulfide-bearing rocks come in all shapes, colors and sizes, she said.

"If you only see white salt, it's probably OK," Buck said.

But if people see colored salt crust, she warned them not to remove it, but to let it neutralize.

The Southern Nevada Water Authority, which has been urging residents to pull out their turf to conserve water, estimates 70 million square feet of grass has been converted to desert landscaping.

Spokesman J.C. Davis said Nevada's alkaline soil acts as a base and neutralizes most acidic reactions before they reach water supplies. The acidic levels and metal concentrations have been stable in washes and Lake Mead for some time, he added.

Buck began her research in 2004, when she studied recently placed rocks at Ed Fountain Park and Del Sol and Canyon Springs high schools and found heavy metals and copper sulfate in each of the samples. Salts at all three sites neutralized naturally over three months.

Mineral Park Decorative Rock, which provided the rocks Buck studied on school sites, contests her results, and believes the soil and fertilizer are responsible for the acidic reaction.

Robin Mickelson, sales manager for the Kingman, Ariz.-based firm, said the company sponsored its own study that concluded the contamination came from outside sources. He called Buck's study flawed because she didn't test directly from the quarry.

"We can't attest for anything once it's left our pit and gone to a job site," Mickelson said.

Salt crusts are apparent across the Las Vegas Valley in areas where there is no decorative rock, he said.

"Our company has been in the decorative rock business since 1974. None of this came to surface until two years ago, when one of our competitors tried to get us out of the market," Mickelson said.

That competitor, Kalamazoo Materials, of Tucson, Ariz., contributed $5,000 to the $23,918.75 grant funding Buck's research.

Bob Linsell, a geologist with Kalamazoo, said he contacted Buck after the company noticed colored salt crust on landscaping rocks in Las Vegas. Kalamazoo officials were looking to expand their mining operations and wanted to know what caused the crust before they settled on a new quarry, he said.

"If it's going to be decorative rock, it needs to be decorative, not something that's an eyesore" Linsell said.

He said he's not trying to run Mineral Park out of business. The money the company contributed to the grant had no strings attached and was paid to the University of Nevada, Las Vegas Foundation. That, along with federal and local government dollars, paid for Buck's project.

Buck said she also tested the rocks before they were placed in soil from a large pile that Mineral Park had dropped in the parking lot of Del Sol, which was under construction at the time. She tested the soils separately and found low metal concentrations, meaning they were not the cause of the high metal contamination.

She said Mineral Park's study did not allow for the pyrite to react to water as it does in a natural setting. Her research was peer-reviewed and will be in the September issue of Soil and Sediment Contamination, an international journal.

Upon identifying the acidic reaction at several schools, "I recommended it not be pulled out because by then we figured out the reaction had already ceased," Buck said.

The school district conducted another study on the salts and found no toxic or hazardous materials present that would be harmful to children.

"The end reports and studies came back and, quite frankly, there was nothing determined to be dangerous for human, animal or fowl," said Dave Broxterman, administrative manager for facilities at the school district.

But, as a result of Buck's study, he said, school officials developed sulfide level limitations on all future orders of landscaping materials "to go the extra mile."