Norsk versjon
THE ORE DATABASE
Occurence 5006 - 020 Grunntjørna I
(Object Id: 291)
(Last updated: 16.02.2005)
Location
County: Trøndelag Municipality: Steinkjer (5006)
Map 1:50000: Holden (1623-2) Map 1:250000: Namsos
Coordinate system: EU89-UTM Zone 32
East: 595143 m. North: 7102548 m.
Longitude: 10.9479610 Latitude: 64.0366100
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Resource
Resource Type: Ferrous metals(Fe, Mn, Ti) Resource Subtype: Iron
Element(s): Fe
Importance
Raw material meaning: Little Importance (reg. 18.02.2015)

Resources and production
Activity: Pitting Reserves:
Operating method: Open pit and underground mining Historical production:


Operations
From - To Activity Comments
1908 - 1910 Geophysics
1910 - 1910 Core drilling
1952 - 1952 Geophysics
1953 - 1953 Geophysics

Mineralization
Era: Paleozoic Period: Ordovician
Genesis: Volcex Form: Ruler
Main texture: Banded Min. distribution: Massive (>50 % ore minerals)
Main grain size: Fine grained (< 1 mm) Main alteration: Skarn formation
Strike/Dip: 350 / 45 Direction: 20
Plunge: 10
Stratigraphic classification of host rock
Era: Paleozoic Period: Ordovician
Province: Caledonides
Geotec.unit: Trondheim Nappe Complex
Tectonic complex:
Igneous complex:
Group: Fosdalsgruppen Formation:

Mineralogy
Relationship Mineral Amount
Gangue mineral Amphibole Major mineral (>10%)
Gangue mineral Pyroxene Subordinate mineral (1-10%)
Gangue mineral Plagioclase Subordinate mineral (1-10%)
Gangue mineral Epidote Subordinate mineral (1-10%)
Gangue mineral Calcite Subordinate mineral (1-10%)
Ore mineral Magnetite Major mineral (>10%)
Ore mineral Pyrrhotite Subordinate mineral (1-10%)
Ore mineral Pyrite Subordinate mineral (1-10%)
Ore mineral Chalcopyrite Accessory mineral (<1%)

Lithology:
Relationship Rock Origin
Host rock Tuffittisk skifer Extrusive
Original rock :Tuff
Metamorphic facies :Greenschist

Structures
Location: Type: Orientation(360 gr.): Relation to min.:
Host rock Fold axis Strike/Dip :20 / 10 Post-mineralisation ;...Effect :Controls
Host rock Foliation Strike/Dip :350 / 45 Post-mineralisation ;...Effect :None

Information(s) in free text format
Free text
Mineraliseringene ved Grunntjørna ble funnet i 1908 og magnetometermåling, røsking og diamantboring ble foretatt 1908-1910. Ørngruben ligger NØ for Grunntjørna og er drevet på sansynligvis samme foldete jernformasjon som i Waldemargruben i Ø og Hagengruben og Hans- Hermangruben i V. ØRNGRUBEN består av flere skjæringer og stoller. Hovedforekomst: 15 m lang skjæring som ender i en 10 m lang stoll mot N (250 m3 tipp). Stollen er drevet langs en nedfoldet (åpen fold) jernformasjon på 2 m mektighet, foldeaksen er 20/10. Den finkornete massive magnetittmalmen (prøve 03 og 04) inneholder noe sulfider og øyne og bånd av epidot. Det er en del lavgehaltige partier innen malmsonen. I sideberget er det tuffittisk skifer.

Bibliography:
From NGU's Reference Archive:
Singsaas, P.; Brækken, H. , 1954
Magnetisk kartering Grunntjern, Malm.
;Norges geologiske undersøkelse;RAPPORT;NGU-rapport; No.97;9 pages

Fieldsamples
Sample No. Sample type Miscellanrous
NT0339.03 Bedrock
Sampler: Wilberg, R.
Comment: Fine grained, massive magntite ore with a little sulphide. Eyes and bands of epidote.
No. of registrated element analyses = 1
NT0339.04 Bedrock
Sampler: Wilberg, R.
Comment: Fine grained, massive magntite ore with a little sulphide. Eyes and bands of epidote.
No. of registrated element analyses = 1
NB! All analyse values are shown at the end of the printout.:

Name of Locality: Grunntjørna I, Skjerp 1
(Object Id: 502 20,01,00)
Location
County: Trøndelag Municipality: Steinkjer (5006)
Map 1:50000: Holden (1623-2) Map 1:250000: Namsos
Coordinate system: EU89-UTM Zone 32
East: 594750 m. North: 7102763 m.
Longitude: 10.9400540 Latitude: 64.0386460
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Resource
Resource Type: Ferrous metals(Fe, Mn, Ti) Resource Subtype: Iron
Element(s): Fe
Resources and production
Activity: Pitting Reserves:
Operating method: Historical production:


Information(s) in free text format
Free text
Vestligste skjerp er en 20 m lang og 3 m dyp røsk (50 m3 tipp). 1,2 m mektig, finkornet, massiv (semimassive partier inniblant) magnetittmineralisering med mm-mektige sulfidbånd (prøve 01). Noe kalkspat amfibol og epidot i malmen. Grønnlig tuffitt med svovelkis-bånd i ligg (prøve 02).

Fieldsamples
Sample No. Sample type Miscellanrous
NT0339.01 Bedrock
Sampler: Wilberg, R.
Comment: Fine grained, massive magnetite ore, banded with pyrrhotite, pyrite and chalcopyrite.
No. of registrated element analyses = 1
NT0339.02 Bedrock
Sampler: Wilberg, R.
Comment: Greenish tuffite, banded with pyrite bands.
No. of registrated element analyses = 1
NB! All analyse values are shown at the end of the printout.:

Name of Locality: Grunntjørna I, Skjerp 2
(Object Id: 503 20,02,00)
Location
County: Trøndelag Municipality: Steinkjer (5006)
Map 1:50000: Holden (1623-2) Map 1:250000: Namsos
Coordinate system: EU89-UTM Zone 32
East: 594819 m. North: 7102732 m.
Longitude: 10.9414570 Latitude: 64.0383550
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Resource
Resource Type: Ferrous metals(Fe, Mn, Ti) Resource Subtype: Iron
Element(s): Fe
Resources and production
Activity: Pitting Reserves:
Operating method: Historical production:


Information(s) in free text format
Free text
20 m lang overgrodd avrøskning av overdekket. Ingen tipp eller blotning.

Name of Locality: Grunntjørna I, Skjerp 3
(Object Id: 504 20,03,00)
Location
County: Trøndelag Municipality: Steinkjer (5006)
Map 1:50000: Holden (1623-2) Map 1:250000: Namsos
Coordinate system: EU89-UTM Zone 32
East: 594989 m. North: 7102672 m.
Longitude: 10.9448980 Latitude: 64.0377700
Show on map
Resource
Resource Type: Ferrous metals(Fe, Mn, Ti) Resource Subtype: Iron
Element(s): Fe
Resources and production
Activity: Pitting Reserves:
Operating method: Historical production:


Information(s) in free text format
Free text
To nærliggende røskegrøfter. Ingen mineralisering.

Name of Locality: Grunntjørna I, Skjerp 4
(Object Id: 506 20,04,00)
Location
County: Trøndelag Municipality: Steinkjer (5006)
Map 1:50000: Holden (1623-2) Map 1:250000: Namsos
Coordinate system: EU89-UTM Zone 32
East: 595119 m. North: 7102492 m.
Longitude: 10.9474450 Latitude: 64.0361200
Show on map
Resource
Resource Type: Ferrous metals(Fe, Mn, Ti) Resource Subtype: Iron
Element(s): Fe
Resources and production
Activity: Pitting Reserves:
Operating method: Historical production:


Information(s) in free text format
Free text
5 m lang stoll (20 m3 tipp) på et litt lavere nivå i lia enn hovedforekomsten. 50 m mektig steiltstående jernformasjon.

Name of Locality: Grunntjørna I, Skjerp 5
(Object Id: 505 20,05,00)
Location
County: Trøndelag Municipality: Steinkjer (5006)
Map 1:50000: Holden (1623-2) Map 1:250000: Namsos
Coordinate system: EU89-UTM Zone 32
East: 595234 m. North: 7102460 m.
Longitude: 10.9497680 Latitude: 64.0358040
Show on map
Resource
Resource Type: Ferrous metals(Fe, Mn, Ti) Resource Subtype: Iron
Element(s): Fe
Resources and production
Activity: Pitting Reserves:
Operating method: Historical production:


Information(s) in free text format
Free text
25 m lang, opptil 5 m dyp røsk som i nordenden ender i en gjenrast stoll. 200 m3 tipp. Minst 2,5 m mektig malmsone med hyppige epidot-pyroksen-amfibol-bånd i malmen. Også mye pyroksenkrystaller (1-2 mm) fordelt i den finkornete jernmalmen (prøve 05 og 06).

Fieldsamples
Sample No. Sample type Miscellanrous
NT0339.05 Bedrock
Sampler: Wilberg, R.
Comment: Fine grained magnetite ore with chrystals of pyrite and bands of epidote, pyroxene and hornblende.
No. of registrated element analyses = 1
NT0339.06 Bedrock
Sampler: Wilberg, R.
Comment: Fine grained magnetite ore with chrystals of pyrite and bands of epidote, pyroxene and hornblende.
No. of registrated element analyses = 1
NB! All analyse values are shown at the end of the printout.:

Analyse Results
from
Deposit Area 5006 - 020 Grunntjørna I

Element analyses
( *=parts pr. million, #=parts pr.billion, Negative values means below detection limit value.)
Sample No. Sample Type Cu* Zn* Pb* Co* Ni* Ag* Au#
NT0339.01 Bedrock 433 190 3 84 171 .3 3.0
NT0339.02 Bedrock 152 21 9 33 16 .1 1.0
NT0339.03 Bedrock 157 21 2 21 22 .2 1.0
NT0339.04 Bedrock 102 24 2 18 24 .2 2.0
NT0339.05 Bedrock 64 9 2 103 21 .1 12.0
NT0339.06 Bedrock 1044 10 3 169 31 .5 10.0
------------------
Sample No. Pt# Pd# As* Cd* Ba* Mo* Sb* Bi* S%
NT0339.01 2.0 3.0 3 .2 2 1.00 2 2 6.89
NT0339.02 3.0 3.0 7 .3 7 4.00 2 2 .74
NT0339.03 1.0 1.0 2 .2 2 1.00 2 2 .08
NT0339.04 1.0 1.0 2 .2 3 1.00 2 2 .26
NT0339.05 3.0 2.0 13 .2 1 1.00 2 2 4.24
NT0339.06 1.0 1.0 22 .2 10 48.00 2 2 5.98
------------------
Sample No. V* Cr* Mn* Fe% Th* U* W* Sr* La*
NT0339.01 37 20 659 31.68 2.00 5.00 1 2.0 2.00
NT0339.02 10 32 213 2.27 12.00 5.00 1 23.0 13.00
NT0339.03 69 9 525 33.37 1.00 5.00 1 3.0 2.00
NT0339.04 65 12 668 31.10 1.00 5.00 1 6.0 2.00
NT0339.05 12 11 327 36.03 1.00 5.00 1 1.0 2.00
NT0339.06 29 37 375 33.57 1.00 5.00 1 6.0 4.00
------------------
Sample No. B*
NT0339.01 2
NT0339.02 3
NT0339.03 2
NT0339.04 2
NT0339.05 2
NT0339.06 2

The fact sheet was created on 22.12.2025
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