Crews have begun exploratory drilling for uranium in Pittsylvania County, which sits atop the richest uranium deposit in the country.

Mike Abbott with the Virginia Department of Mines, Minerals and Energy says Virginia Uranium Incorporated began drilling near Chatham this week.

There's been a moratorium on uranium mining in Virginia for 25 years, and he says the state permit is only for exploration.

Geologists will look at the core and determine the type of rock, thickness, and test the rock for minerals such as uranium.

The company has permission to drill 40 holes over a one-year period and take core samples. Twenty of the holes are new and crews will re-drill 20 holes first opened during exploratory drilling in the early 1980s.

The uranium deposit under Pittsylvania County is estimated at up to 110 million pounds. There are smaller deposits in several other Virginia counties, including Madison, Culpeper and Orange.