At the Erzberg in Hüttenberg, Carinthia possibly the Romans already dug for the "noric iron"("ferrum noricum"). The iron is  bound here in oxide form or occurs carbonatic as the mineral siderite. Siderite accompanies the here occurring blue chalcedony which has been formed in cavities in several centimetres thick layers.

The chalcedony was processed century in 18 and 19 to small arts and crafts items (Hacquet, B.v., 1784). The chalcedony shows rare a banding mostly it is just translucent and greyish-blue. It is often paired with Siderite, which occurs in yellowish-brown, rhombohedrical crystals. The present piece is showing pseudomorphs formed in chalcedony after fibrous aragonite crystals in brushy clusters.

Source: Hacquet, B.v.,(1784), Hacquet´s mineralogisch-botanische Lustreise, von dem Berg Terglau in Krain, zu dem Berg Glockner in Tyrol, im Jahr 1779 und 1781. - Wien, J.P. Kraus