002.46.Idrija

Idrija Municipal Museum, Prelovčeva 9, SI-5280 Idrija

Public

Municipality of Idrija, Mestni trg 1, SI-5280 Idrija

510:IDR;G-1008

Ore deposit

The sample is poor coral ore. The rock is almost black bituminous quartz Skonca sandstone, rich with Brachiopod shell residues of the genus Discina. The shells measure up to 1 cm, have a typical bituminous glow and are poorly mineralised with cinnabar.

Length 17 cm, width 15 cm, height 6 cm.

Flint sandstone, Brachiopod shells, syngenetic cinnabar mineralisation.

Triassic - Ladinian, the highest level of Skonca beds.

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Because of the substitution of the Discina brachiopod shell residues with the coral residues, the Idrija Miners named the ore with the Discina residues – the coral ore. The name was used in geologic literature for the first time by Joannes A. Scopoli (1761). The base rock is flint sandstone in which differently dense Brachiopod shell residues are included. Flint sandstone with Discina is the highest level of Skonca beds in Idrija ore deposit. Under the flint sandstone, the bituminous marls and slates are located, and pyroclasts above it. During the time of formation of the sand level of the flint sandstone, the second phase of hydrothermal activity in the Idrija Mid-Triassic tectonic rift was gradually ending. Simultaneously with the quartz grains, the water also deposited mineralised chalcedony grains and mineralised radiolaria. Different syngenetically mineralised coral ores were formed – from extremely rich to poor ones. In the final tectonic phase, the coral ores were, in some places, still faulted and fractured and epigenetically mineralised with cinnabar and native mercury. In the second half of the 19th century, the coral ore, poor in cinnabar, became economically interesting because of the phosphates and fluorine (artificial fertilisers), related with Brachiopod shells.

The described coral ore is being preserved, secured and presented as important natural heritage of mining in Idrija with exceptional universal values. The specimen represents one of the natural features of Idrija ore deposit. It is a part of the geological collection of Idrija Municipal Museum. Visitors can view it within the permanent museum exhibition “Five Centuries of the Mercury Mine and the Town of Idrija”. It can also be used for different types of mercury heritage promotions.

Idrija ore deposit, lower pit, VII horizon, mining field Hangend VII/7.

Idrija Municipal Museum, Gewerkenegg Castle (showroom 3).

The specimen is appropriately preserved. The entire geological collection was professionally completed and placed in the renovated premises of the Idrija Municipal Museum in 1992. Therefore, no additional interventions are necessary. Security of the premises is taken care of.

good

Regular seasonal maintenance.

- Inventory Book of the Idrija Municipal Museum.

Mestni muzej Idrija

Miha Kosmač

1. 3. 2018

Never