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	THE ORE DATABASE
	Prospect 3316 - 022 Skuterud Nordgruver
	(Object Id: 5903) (Last updated: 16.03.2020)

Products

	Element/product	Crude ore grade or quality	Reg. date
	Co	0.2 %	31.08.2010

Mineralization

	Genesis:		Form:
	Main texture:		Min. distribution:

Main grain size:

Main alteration:

	Strike/Dip:		Direction:
			Plunge:

Stratigraphic classification of host rock

Era:

Period:

	Province:
	Geotec.unit:
	Tectonic complex:
	Igneous complex:

Group:

Formation:

Information(s) in free text format

Free text

The cobalt ores at Skuterud were found in 1772, and ordinary production started in 1776. First in large open pits, but from 1827 until the closure in 1898, mining was done underground. In the 1890s, ore reserves decreased rapidly, leading to the final shutdown of mining operation in 1898. On the basis of different old mining reports the total production is estimated to 1 Mt with 0.2 % Co. In addition to cobalt, the ores contain significant grades of copper (up to 1-2 %) and locally enrichment of gold (several ppm). The cobalt occurrences at Modum are related to sulphide-rich schist zones, so-called fahlbands. The most extensive sulphide-rich zone has a length of 12 km along strike, and is up to 100–200 m wide. The rock type hosting the sulphides may be characterized as a quartz-plagioclase-tourmaline-phlogopite-sulphide gneiss or schist. Graphite is locally common and its content may attain more than 5 % of the rock. The cobalt mineralisation is, to a large degree, characterised by impregnation of cobaltite (CoAsS), glaucodote ((Co,Fe)AsS), safflorite ((Co,Fe)As2) and skutterudite (CoAs3), which partly occur as enriched in quartz-rich zones and lenses. The cobalt-rich lenses are structurally controlled, following axes of folds and lineations in the area.

Photo(s) from the Deposit area:

Photo no. 1 showing Nordgruvene" Photo no. 2 showing Erythrin"

Bibliography:

From NGU's Reference Archive:

Grorud, Hans-Fredrik , 1997

	Textural and compositional characteristics of cobalt ores from the Skuterud Mines of Modum, Norway

;Norsk geologisk forening;TIDSSKRIFTARTIKKEL;Norsk geologisk tidsskrift; No.77 (1);31-38 pages

Abstract:

The metasedimentary rocks of the Modum Complex contain concordant, sulphide- rich zones, commonly referred to as 'fahlbands'. Two of these fahlbands contain cobalt minerals. Petrographic and microprobe analyses of the cobalt minerals have been performed on selected samples, to gain insight into the genesis and post-mineralization history of the cobalt minerals. It is suggested that these minerals precipitated from an oxidizing fluid, and that certain minerals in the uraninite.thorianite series precipitated simulataneously. The fahlband silicates, and later the cobalt minerals, were recrystallized during Sveco- norwegian penetrative deformation and thermal maximum (-1.2- -0.9Ga). Prolonged heating during this event eradicated any compositional zoning which may originally have been present. Neither textural nor mineral chemical analyses indicate whether the observed cobalt minerals are the result of a primary precipitation, or of remobilization.

Name of Locality: Gruve 6

(Object Id: 32742 22,01,00)

Location

County:

Buskerud

Municipality:

Modum (3316)

Map 1:50000:

Hokksund (1714-1)

Map 1:250000:

Skien

Coordinate system:

EU89-UTM Zone 32

East:

548292 m.

North:

6649459 m.

Longitude:

9.8652970

Latitude:

59.9796440

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Resource

	Resource Type:	Ferroalloys (Cr,Ni,Co,V,Mo,W)	Resource Subtype:	Cobalt
			Element(s):	Co As

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The fact sheet was created on 26.04.2024

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