In 1971, estimated ore reserves within the limits of the planned open pit were approximately 900 million tonnes of ore averaging 0.48% copper and 0.55 grams of gold per tonne. It was expected that the concentrate to be shipped would contain approximately 30% copper, 1 ounce gold per tonne and some silver. The orebody, which contained copper, gold and silver, was situated on a special mining lease of over 37 square kilometres held by Bougainville Mining Limited (now Bougainville Copper Limited — BCL)

Mining was carried out by blasting the orebody, removing the ore from a series of benches by electric shovels and hauling it by trucks to a primary crusher adjacent to the pit. Waste material was similarly removed and hauled to waste dumps near the pit.

Coarse ore from the primary crusher was transported by a conveyor system to the concentrator, which was situated near the mine. The concentrator used a conventional crushing grinding and floatation process for the production of copper concentrate. It had ten ball mills, which gave a nominal capacity to treat 100,000 tonnes of ore per day. The concentrate was thickened and pumped 27 kilometres through a 150-millimetre diameter pipeline to the port at Anewa Bay . Here the concentrate was dried to approximately 8% moisture and stored ready for shipping. The mine and concentrator were operated on a 24 hours per day, 365 days per year basis.

During 1972, a total of 46,753,200 tonnes of ore and waste was extracted from the mine. Of this 21,885,252 tonnes of ore were milled, and 123,961 tonnes of copper were produced. In 1973, actual production of 182,890 tonnes of contained copper in concentrate exceeded the 1973 production target. 1974 saw a total of 56,000, 525 tonnes of ore and waste removed from the mine. Of this 30,142,669 tonnes of ore were milled and from this, concentrates containing 184,083 tonnes of copper were produced.

During 1976 the diamond drilling program within the Special Mining Lease continued. It was aimed at a fuller evaluation of ore reserves within the lease. Continued metallurgical improvements produced the highest concentrate grade since startup.

Shipments for 1977 totalled 614,819 dry tonnes of concentrate. Production of contained copper in concentrates totalled 182,291 tonnes. In October 1978 sales of copper concentrates since start up passed the 4 million tonne mark.

The level of measured ore reserve of the ore body continued to decline and BCL saw a need for further exploration in areas surrounding the Special Mining Lease. It held Authorities to Prosper over nearby areas of interest, but the Bougainville Mining Agreement provided that exploration could not commence until government approval was obtained. Investigations were determining if copper could be economically extracted from waste dumps by leaching, and if additional gold could be recovered from tailings.

In 1979 gold production since commencement of operations reached 150,000 kilograms. Copper production from 1972 to 1980 reached 1.5 million tonnes. The government restriction on mineral exploration on Bougainville Island remained in force. When the drilling program in the north east corner of the Special Mining Lease was completed, the results indicated no extension of the ore body.

When the initial evaluation of the Panguna orebody was undertaken, the presence of gold in the ore, although in only small quantities, was recognised as a substantial benefit to the viability of the proposed large tonnage copper mining operation. Despite the low grade of gold in the ore, the massive scale of mining operations resulted in BCL being ranked high on the list of the world's gold producers. In fact the mine on Bougainville was the largest single gold source in the non-Communist world outside South Africa . The rise in the price of gold was reflected in the contribution that gold made to the gross revenue of BCL. From a level of 16% in 1972, the contribution of gold increased to 46% of BCL's gross revenue in 1980. Thus from the status of a by-product when the mine was first conceived and brought into production, gold developed to a position of almost equal importance with that of copper.

After the first decade of operations (1972-1981) the total production from the mine was 1.7 million tonnes of copper, 188 tonnes of gold and 433 tonnes of silver. This production had a value of K2.4 billion which represented 48% of the country's exports.

In 1981 the program of diamond drilling to test the grade of mineralisation below the present planned pit bottom continued. The government restrictions preventing exploration outside BCL's mining lease remained in force.

BCL was among the leaders in the mining and mineral processing industry in applying technological innovations to production processes. Extensive use was made of computer systems in the area of process development and control, instrumentation, materials handling, equipment design and wear part technology.

The recoverable proved ore reserves at the end of 1989 are estimated at 496 million tonnes of average grade 0.42% copper and 0.55 grams per tonne gold. The recovery of this ore would require the mining of an additional amount of measured mineral resource, which is estimated at 520 million tonnes 0.22 copper and 0.18 grams per tonne gold. Since inception until cessation of operations on 15 May 1989 the mine produced concentrate containing 3.1 million tonnes of copper, 306 tonnes of gold and 783 tonnes of silver. The production had a value of K5.1 billion which represented approximately 44 % of Papua New Guinea 's exports over that period.