MOSCOW – Russian scientists said Monday they had established the composition of the meteorite that exploded over the Chelyabinsk region last week, injuring hundreds of people and causing millions of dollars worth of damage.

Over the weekend, scientists collected 53 tiny pieces of dark porous material that were recovered by local residents near Chebarkul Lake, 60 miles west of Chelyabinsk, the regional center, officials said. The biggest of the finds was 7 millimeters long.

Not everyone who found the objects turned them in, apparently: Some enterprising locals were offering what they claimed to be fresh meteorite pieces for sale online for as much as $10,000 apiece. Some attributed far-reaching (if bogus) powers to the space rocks.

“Improves male potency, reduces weight,” one ad claimed. “Trade in for a car or real estate a possibility.”

The pieces collected by scientists were described as bits of chondrite, a type of stony meteorite, which contained at least 10 percent metallic iron and nickel alloy as well as chrysolite and sulfite, according to Viktor Grokhovsky, a member of the Russian Academy of Sciences meteorite committee.

“We are certainly dealing with the debris of the object that traveled here from outer space,” Grokhovsky, a professor at Yekaterinburg-based Urals Federal University, said in a phone interview. “We sent our team to the lake as soon as we heard of the meteor falling, as it is extremely important to find and study fresh debris.”

The meteorite, estimated at 55 feet wide and 10,000 tons, exploded in the atmosphere Friday with the power of several nuclear bombs.

Shock waves shattered more than 1 million square feet of window glass, local officials said. Hundreds suffered minor injuries.