In 1934 there was a new increase of the wolfram prices and consequent growth of the activity in the three main exploration areas of the concession (Panasqueira, Barroca Grande and Rio). This cycle associated with the Second World War was remarkable with 750 workers in 1934; 4,457 in 1942 and 10,540 workers in 1943. The Plant at Rio reached a capacity of 300 t per day and Panasqueira 1,000 t per day. The monthly production of concentrates reached 300 t, more than the rest of the country. It is at that time that the connection is made Underground from Barroca Grande to Panasqueira. At the time of the Second World War, Panasqueira was the largest mine in the country and one of the largest wolfram mines in the world. The price of the wolfram dropped drastically at the end of the Second World War, only increasing again in 1950 due to the Korean War. During this period there was a great modernization of the company with the introduction of scrapers and mechanical loaders. Mules were replaced by locomotives. The production of cassiterite was increased to compensate the low prices of wolfram. The production of copper concentrates began in 1962.