Iron ore was first crushed, roasted and agglomerated and then charged into the blast furnace.   Ore in the size of a fist was the best for charging. Special mills were used for crushing. Water was released when limonite ore was roasted, while roasting of  siderite ore caused decomposition of carbonates and transition of siderite to hematite. Red dust was released during that process, which was so significant of Jesenice that it was called the town of red dust. During agglomeration small and fine granular ore stuck together into bigger pieces. In Jesenice ore mills, roasting furnaces and agglomeration were located in Hrenovica, the area between Stara Sava and Bohinj railway. In 2020 the mill was renovated within Naša industrijska dediščina naš ponos (Our industrial heritage – our pride) Project.

Ore crushing in 1968