Prospect Resources (ASX:PSC) upgraded its mineral resource estimate for the Mumbezhi project in Zambia, according to a Wednesday filing with the Australian bourse.

The mineral resource estimate for the project now stands at 208.1 million tonnes at an average grade of 0.4% copper from 173.8 million tonnes at 0.4% copper.

The updated indicated and inferred mineral resource delivered a 20% increase in tonnage, including 106% increase in gold and 14% increase in copper, the filing said.

Meanwhile, the company began its third phase diamond drilling targeting further mineral resource expansion at the southern end of the Nyungu Central deposit, per the filing.

Shares fell nearly 2% in morning trade Wednesday.