The Erzberg is the biggest open pit iron ore mine in middle Europe and the biggest deposit of siderite in the world. The main iron mineral is correctly identified as sideroplesite with iron content between 38 and 42 %. Other iron minerals are ankerites with differing iron content between 10 and 17 %. The main waste materials within the ore bearing formation beside of ankerite are different types of limestone. The bottom floor of the deposit is formed by a volcanic silicate rock and the overburden by a partly schisted sandstone called “Werfener Schichten”.
According to historic documents the mining activity was first mentioned in 712, so there is a mining history for longer than 1300 years. These first mine operations were many small open pit mines which mainly extracted the weathered parts of the ore body. In the 16th century the first bigger underground operations started using mallet and gad. The modern open pit operation started in 1820 and since 1890 the characteristic pyramidal form took shape.
In 1907 there were 60 benches in operation with 12 m height and in 1928 the number of benches was halved to 30 with 24 m height which is the today’s appearance. Nowadays over 11 million tons of ore and overburden are blasted every year by the VA Erzberg GmbH at the Erzberg in order to produce 2.8 million tons of sinter fines for the voestalpine sinter plants in Linz and Donawitz (Austria). To meet the product quality production control starts already in the open pit by selective mining of three raw material qualities depending on the iron content. The production control starts with the layout of the blasting systems on the basis of the deposit model. The model includes data of the chemical analyses of the production drill holes, exploration drills and geological data of the old underground mine surveying. The model delivers a quality forecast for the planned blasting system which assists the schedule for drilling and blasting operation. The chemical data from the drilled holes are fed back into the model so the forecast precision increases. After the blast additional samples could support the raw material classification. That system ensures that every time every raw material quality is available for best utilization of vehicle fleet and processing plant.
The location of the mine within the city of Eisenerz requires special techniques to assure low environmental impacts. Additionally the geological situation of the orebody is a challenging issue for the mining engineers and therefore selective mining processes have to be applied.