Shares in Petra Diamonds (PDL.L) rise 5 percent after the company completes a $120 million share placing , which it says will be used to double its stake in its flagship Cullinan mine in South Africa, cut debt and expand output.

Petra Diamonds CEO Johann Dippenaar holding a 26.58 carat rough blue diamond - Photo: www.petradiamonds.com

"The benefit to the company is that it is now significantly more leveraged to increased diamond prices given the higher exposure to Cullinan," says Ambrian in a note.

The broker, which repeats its "buy" rating, says cutting debt "de-risks expansion significantly as previously there was the potential of capital constraints" and, although Petra does not present "a quick buck investment ... the company does remain one of the top picks in the small-cap mining space".