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Gruvberget, Hudikvall, Sweden

To start with the location: there are several Gruvberget in Sweden, this one is in Hudiksvall province with Bricka being the closest town. There are few small old mines at the Gruvberget, the samples here were taken at SWEREF99TM 686951/582336 which is the lowest of the five catalogued mines there. The ore mainly consists of magnetite, followed by ilmenite with some minor pyrite and chalcopyrite. The magnetite shows lamellae of spinel and ilmenite and the ilmenite shows lamellae of hematite and spinel, sometime in more than one generation. By simple ore microscopy it is very difficult to figure out. Gruvberget and the related Bläckmyran deposit recently moved into focus due to the high vanadium content of the ore.

Polished slab of the typical ore (14 cm wide):

Gruvberget113

Simple ones first: pyrite. Nic //, Obj. 20x, air, 100 µm bar:

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Chalcopyrite. Nic //, Obj. 20x, air, 100 µm bar:

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Ilmenite with hematite exsolution lamellae. Nic //, Obj. 20x, air, 100 µm bar:

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The same, rotated by 90°:
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The same, rotated by 90°, Nic +, Obj. 20x, air, 100 µm bar:

image_0000503

The same, rotated by 90°:

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And finally a look to the magnetite, with spinel lamellae, and more or less invisible ilmenite lamellae. Nic //, Obj. 20x, air, 100 µm bar:

image_0003012

The same under Nic + reveals the ilmenite lamellae:

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For further informations on the region this article might be interesting:

Ros F., Lindblom, L.: Vanadin-titanfyndigheten Gruvberget. SGU Rapport PRAP 83560