Anglo American, one of the world's largest mining groups, reported mixed production results in the second quarter as increases to copper, platinum and diamond output were offset by declines in iron ore, coal and nickel.The company said that in the three months to the end of June, spending on exploration and evaluation totalled $132m, a drop of 24% when compared with last year.Through its 69.7% shareholding in the South African supplier of seaborne iron ore, Kumba Iron Ore, Anglo saw iron ore production from Kumba's three mines in the country fell by 1.0% year-on-year to 11.3m tonnes, as weaker production at Sishen - as it continues to recover from stock drawdowns during strikes late last year - was offset by better results at Kolomela.Output of metallurgical fell by 9.0% to 4.4m tonnes. The company said this due to "strategic production cuts" in anticipation of weakening market conditions, a planned longwall move at Moranbah and recovery at Dawson following poor weather conditions in the first quarter. Export thermal coal in both South Africa and Colombia declined by 5.0% and 3.0%, respectively.Nickel production dropped 22% over the year to 8,500 after production at its Loma de Niquel project in Venezuala - which produced 3,000 tonnes in the second quarter of 2012 - came to an end in November.Copper production meanwhile increased by 14% to 182,900 tonnes helped by higher output across all businesses except the Mantoverde project in Chile. The company maintained its full-year production guidance of 680,000 tonnes but warned that realised prices were down significantly at 318 cents a pound in the first half, compared with 370 cents a pound the year before."Intermittent illegal industrial action" wasn't enough to hold back the production of platinum during the second quarter, which rose 2.0% to 594,000 ounces. Meanwhile diamond output - through its 85% stake in diamond firm De Beers - rose 10% to 7.9m carats due to improved grades at the Orapa and Jwaneng mines in Botswana.In other asset classes, phosphates production increased by 15% to 312,300 tonnes, while niobium output fell 8.0% to 1,100 tonnes.