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Ontario Geological Survey
Permanent Link to this Record:
MDI52A10NE00013
| Record Name(s) | Dorion Amethyst - 1991, E.J. Williamson - 1991 |
|---|---|
| Related Record Type | Simple |
| Related Record(s) | |
| Record Status | Prospect |
| Date Created | 1991-Mar-22 |
| Date Last Modified | 2022-Feb-23 |
| Created By | |
| Revised By |
Primary Commodities: Amethyst
Secondary Commodities: Copper, Mineral Specimen, Uranium
Township or Area: McTavish
Latitude: 48° 41' 58.99" Longitude: -88° 36' 34.93"
UTM Zone: 16 Easting: 381558 Northing: 5395326 UTM Datum: NAD83
Resident Geologist District: Thunder Bay South
NTS Grid: 52A10NE
Point Location Description: Field visit with GPS, confirmed with Google Earth
Location Method: Field Visit
Access Description: Access is by means of a gravel road that intersects Highway 11-17 approx. 8 km east of Pearl.
The property was originally staked as a copper prospect. Roy Barker drilled 13 diamond drill holes in 1967 to evaluate the copper mineralization. When Barker dropped the option, the property reverted to Williamson who then promoted the property as an amethyst mine. The vein has produced some exceptional amethyst crystals. Barker's drill core is no longer available for study, and to date no development work, other than some stripping and blasting to expose the amethyst vein, has been done.
| Office File Number | Online Assessment File Identifier | Online Assessment File Directory |
|---|---|---|
| 11 | 52A10NE0035 | 52A10NE0035 |
Province: Superior
Geological Age: Archean
Jun 21, 2017 (Therese Pettigrew) - Sibley Group mudstone and sandstones of the Rossport Formation lie unconformably on Archean quartz monzonite.
| Rock Type | Rank | Composition | Texture | Relationship | Quartz Monzonite | 1 | Host |
|---|---|---|---|---|
| Terrigenous-Clastic-Unsubdivided | 2 | Mudstone And Sandstone | Adjacent |
Jun 21, 2017 (Therese Pettigrew) - Barker's drilling outlined a "breccia" zone near the unconformity. Ten of the thirteen drill holes drilled by Barker in 1967 were drilled into the quartz monzonite. The unconformity has been described in the logs as a "hybrid granitic breccia with leached xenoliths with stringers and seams of sulfides and chlorite". This zone crops out just north of the calcite-amethyst vein on the property, and consists of highly altered fragments of granitic rock imbedded in a matrix of clay and sand. This "breccia zone" represents a pre-Sibley weathered surface. The unit contains finely disseminated pyrite and is stained by a rusty gossan. Immediately overlying this weathered horizon are brecciated mudstones of the Rossport Formation. The mudstone unit is fine grained, tan to dark reddish-brown,in color, and massive. Bleaching has occurred along numerous fractures throughout the outcrop.
| Rank | Mineral Name | Class | Economic Mineral Type | Alteration Mineral Type | Alteration Ranking | Alteration Intensity | Alteration Style |
|---|---|---|---|---|---|---|---|
| 1 | Amethyst | Economic | Ore | ||||
| 2 | Chalcopyrite | Economic | Ore | ||||
| 3 | Malachite | Economic | Ore | ||||
| 4 | Azurite | Economic | Ore | ||||
| 5 | Pyrite | Economic | Ore | ||||
| 6 | Calcite | Economic | Ore | ||||
| 7 | Barite | Economic | Ore | ||||
| 8 | Galena | Economic | Ore | ||||
| 9 | Sphalerite | Economic | Ore |
Jun 21, 2017 (J Scott) - Sibley Grp conglomerate and siltstones at the Archean U/C Malachite, cpy, pyrite amethyst and U (160 ppm U, up to 8% Cu)
Jun 21, 2017 (Therese Pettigrew) - Uranium is associated with faults and fracture systems proximal to the Proterozoic/Archean unconformity. Immediately overlying the weathered horizon at the unconformity are brecciated mudstones of the Rossport Formation. At the Dorion Amethyst Mine, this unit is charged with chalcopyrite and an unidentified radioactive mineral. Uranium has precipitated locally in the vicinity of sulphide minerals. The Dorion Amethyst Mine contains chalcopyrite, amethyst, calcite, and uranium minerals. A spring has its source at the unconformity and emanates from the vein system as well as from a diamond drill hole. This spring reinforces the concept of an active plumbing system. Minor galena and sphalerite were noted in the vein system at the Dorion Amethyst Mine. The calcite-amethyst vein terminates in the mudstone unit. Within the mudstone, and on strike with the calcite-amethyst vein, there are numerous calcite-filled fractures. The calcite vein is not exposed immediately west of the stripped area. Further west and on strike with the main vein, a similar calcite-amethyst vein is exposed in a cliff on the west side of the trail. This may be an extension of the main vein. An examination of the property with a gamma ray spectrometer in 1978 indicated that the copper-rich zone was radioactive. The highest readings were obtained from the chalcopyrite-impregnated, brecciated Rossport Formation. One grab sample yielded 160 ppm uranium and 8.16% copper (Scott, 1987).
| Rank | Classification |
|---|---|
| 1 | Vein |
Map - Geological series, McTavish Township (east part of north half), District of Thunder Bay
Publication Number: P0721 Scale: 1:15,840 Date: 1997
Author: McIlwaine W.H.
Publisher Name: Ontario Dept. of Mines and Northern Affairs
Location:
Mono - Amethyst deposits of Ontario
Publication Number: GB05 Scale: Date: 1998
Author: Vos M.A.
Publisher Name: Ontario Division of Mines
Location:
Mono - Uranium occurrences of the Thunder Bay-Nipigon-Marathon area
Publication Number: OFR5634 Scale: Date: 1987
Author: Scott J.F.
Publisher Name: Ontario Geological Survey
Location:
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For detailed information regarding this mineral record please contact the Thunder Bay South Resident Geologist District Office