Output in the three months was 1,097,523 carats versus 842,796 carats last year due to an increase in undiluted run of mine ore, improving grades and additional production from the Kiberley tailings operation in South Africa.
The group said it continues to expect full year production of between 4.4 and 4.6 million carats.
Revenues for the quarter to September 30 came in at US$94.7 million from 745,447 carats sold. In the first quarter last year, no sale was held.
Petra has interests in five producing operations - three underground mines in South Africa (Finsch, Cullinan and Koffiefontein), the Kimberley operations (including an underground mine and extensive tailings retreatment operations) and one open pit mine in Tanzania (Williamson). It is also exploring in Botswana.
Chief executive Johan Dippenaar said: "The newly established caves at both Finsch and Cullinan, accessing higher grade undiluted areas, are starting to meaningfully contribute to ROM production, which is continuing to ramp-up in line with expectations."
He added that the diamond market was holding firm with prices like for like basis matching those realised in the period January to June 2016 - the group's second half.
Tragically, the firm said, there were four fatalities in the period due to three unrelated incidents.
Dippenaar said: "Petra has always taken pride in excellent safety results posted by its operations. It is therefore with deep regret that we report fatal injuries suffered by four of our employees.
"Across the group, we have embarked upon renewed safety drives to reiterate our zero-tolerance approach to unsafe acts and working conditions with an aim of zero harm to our workforce and contractors."
Shares gained 5.58% to 147.6p each.