Gjerdingen

Thanks to Ragnar Salmén for getting me there 16 years ago and to Svein Arne Berge for trading what I did not find myself. Not to forget Knut Eldjarn, Gunnar Raade and Jan Haug, whose articles are the basis of the following, and again László Horváth for help with the list.

Gjerdingen is a wooded area 30 km N of Oslo, the minerals being found in blocks of ekerite along a forest road. Ekerite is an alkaline or soda granite containing aegirin and alkaliamphibole (riebeckite) with the quartz and feldspar. In the huge Oslo field (eruptive rocks from the Perm with „rift-valley“ intrusions) ekerite is very common, it changes to a syenite (nordmarkite) with reduced quartz contents.

The locality has been known early in the 20^th century for elpidite and astrophyllite, however, serious work didn´t start until 1963, but continues still today. However, nobody found eudialyte so far, but again - it´s an interesting alkaline locality.

Mineral list: (Bold=type locality)

Aegirine

Albite

Allophane

Anatase

Arfvedsonite

Astrophyllite

Bastnaesite-(Ce)

Biotite

Brookite

Catapleiite (?)

Clinochlore

Cryolite

Dalyite

Elpidite

Epididymite

Ferrocolumbite

Fluorapatite

Fluorite

Gagarinite-(Y)

Galena

Gearksutite

Gibbsite

Goethite

Helvite

Hematite

Janhaugite

Kupletskite

Lorenzenite

Marcasite

Microcline

Molybdenite

Monazite-(Ce)

Montmorillonite

Muscovite

Narsarsukite

Neighborite

Nenadkevichite (labuntsovite-nenadkevichite-series))

Opal

Orthoclase

Pachnolite

Phlogopite

Pyrite

Pyrochlore

Pyrophanite

Quartz

Ralstonite

Rhodochrosite

Riebeckite

Rutile

Sellaite

Sphalerite

Stilpnomelane

Sulfur

Thomsenolite

Titanite

Zeophyllite (?)

Zircon

&:Suggested reading:

Raade,G.: Mineralogy of the miarolitic cavities in the plutonic rocks of the Oslo Region, Norway, Mineral.Record, 3(1972), pp.7-11

Raade, G., J.Haug: Rare fluorides from a soda granite in the Oslo Region, Norway, Mineral.Record, 11(1980), pp.83-91

Eldjarn,K.: Drusemineraler fra Gjerdingen i Nordmarka, NAGS-nytt, 8(1981), 2, pp.6-10 (in Norwegian)

Eldjarn,K.: Kryolitt fra Gjerdingen i Nordmarka, NAGS-nytt, 8(1981), 2, pp.11-12 (in Norwegian)

Raade,G.,J.Haug: Morphology and twinning of sellaite from Gjerdingen, Norway, Mineral.Record, 12(1981), 231-232

Raade,G., J.Haug: Gjerdingen: Fundstelle seltener Mineralien in Norwegen, LAPIS 7(1982), 6, pp.9-15 (in German)

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