Ontario Geological Survey
Permanent Link to this Record:
MDI52A10SW00007
| Record Name(s) | 7z - 1890, Crystal Beach Amethyst - 1983, Hilkka - 1984 |
|---|---|
| Related Record Type | Simple |
| Related Record(s) | |
| Record Status | Occurrence |
| Date Created | 1991-Mar-05 |
| Date Last Modified | 2022-Apr-26 |
| Created By | |
| Revised By |
Primary Commodities: Amethyst
Secondary Commodities: Silver, Barite, Fluorite, Zinc, Lead, Copper
Township or Area: Macgregor
Latitude: 48° 32' 52.4" Longitude: -88° 54' 51.61"
UTM Zone: 16 Easting: 358721 Northing: 5378967.99 UTM Datum: NAD83
Resident Geologist District: Thunder Bay South
NTS Grid: 52A10SW
Point Location Description: Central trench
Location Method: Field Visit with GPS
Access Description: Proceed east from Thunder Bay on Highway 11-17. Turn left into Karkkainen’s yard (Fish & Amethyst) across Hwy 11-17 from Crystal Beach Store. Proceed north up gravel road behind house. Approximately 150 m north of highway, gravel road forks. Straight ahead approx. 100-100 m leads to trenching and bulldozed strips, or follow fork to right for approx. 400 m to shaft.
1890: 2 shafts and a number of trenches by Goddard and Chamberlain. 1983: A. Karkkainen carried out stripping. 2014: Amethyst exploration in area of historic trenches by B. Clemons and S. Gurney.
| Office File Number | Online Assessment File Identifier | Online Assessment File Directory |
|---|---|---|
| 2.8596 | 52A10SW0011 | 52A10SW0011 |
Province: Southern
Formation Group: Animikie Group
Geological Age: Paleoproterozoic
May 31, 2018 (Mark Puumala) - The 7Z amethyst occurrence is hosted in a 050-striking vein system/breccia zone that is located approximately at the unconformity between sedimentary rocks of the Paleoproterozoic Gunflint Formation and Archean intrusive rocks of the McKenzie Granite stock. The amethyst-bearing vein system has been exposed in a series of three historic trenches that cover a strike length of 180 m. The portion of the vein system exposed in the southwestern and central trenches is hosted by rocks of the Gunflint Formation, while the veins exposed in the northeastern trench occur at the unconformity and are hosted by both rock types (sedimentary and granite). The width of the zone appears to be approximately 10 m. Gunflint rocks are strongly silicified adjacent to the veins. The majority of the amethyst-bearing veins strike approximately 050 (i.e., parallel to the breccia zone) with near-vertical dip. The vein widths are variable, ranging from centimetre- to metre-scale. In the Gunflint Formation rocks, a near-horizontal set of narrow veins also occurs along bedding plane fractures. A third set of narrow, approximately north-striking veins, was also observed immediately to the south of the main breccia zone in road cuts along the north side of Highway 11-17.
| Rock Type | Rank | Composition | Texture | Relationship | Granite | 1 | Host |
|---|---|---|---|---|
| Terrigenous-Clastic-Unsubdivided | 2 | |||
| Diabase | 3 | Medium-Grained Diabase |
May 31, 2018 (Therese Pettigrew) - The massive quartz porphyritic granite near Highway 11-17 is crosscut by numerous amethystine quartz veins striking approximately 070 degrees. These amethyst veins display well-developed crystals that range in colour from dark purple to a deep pink. Narrow 5-10 cm wide fine-grained felsic dykes parallel the amethyst veins and are offset by minor faults. About half a kilometer north of the massive granite outcrop, two mafic rock types have been exposed by mechanical stripping. The Gunflint rocks are quite fine-grained and have the appearance of a jasperitic or hematitic chert. The medium-grained diabase has a distinct bluish tinge. These mafic rocks are intruded by numerous amethystine quartz veins trending approx. 065 degrees. Veins ranging from a few mm to 2 m in width contain minor concentrations of calcite. The larger veins contain light purple amethyst crystals up to 5 cm in length. Locally 1-2% pyrite occurs as spherical to elliptical blebs (Hazard Land Report – 1984 in Thunder Bay RGP MDI files).
| Rank | Mineral Name | Class | Economic Mineral Type | Alteration Mineral Type | Alteration Ranking | Alteration Intensity | Alteration Style |
|---|---|---|---|---|---|---|---|
| 1 | Argentite | Economic | Ore | ||||
| 2 | Barite | Economic | Ore | ||||
| 3 | Chalcopyrite | Economic | Ore | ||||
| 4 | Fluorite | Economic | Ore | ||||
| 5 | Galena | Economic | Ore | ||||
| 6 | Silver | Economic | Ore | ||||
| 7 | Sphalerite | Economic | Ore |
May 31, 2018 (Mark Puumala) - The amethystine quartz in this vein system shows a wide variation in colour ranging from light pink (i.e., rose quartz), through to deep purple. Colourless to white quartz and smoky quartz are also abundant. Veins hosted by granite tend to contain lighter-coloured amethyst, while deep purple amethyst and smoky quartz are most likely to be found in the southwestern trench, which is hosted by Gunflint formation rocks. Most amethyst crystal points are on the order of 1 cm wide. However, much larger crystals were observed in some vugs. Crystals hosted in the Gunflint rocks commonly have a surface coating of hematite.
May 31, 2018 (Therese Pettigrew) - A sample collected by G. Patterson, OGS staff member, in 1984 assayed <0.01 opt Au and <0.01 opt Ag (Thunder Bay RPG MDI files). The Weekly Herald (Aug 9, 1890) reported that No. 7Z was “a veritable mountain of amethyst with rich surface signs of silver”.
| Rank | Classification |
|---|---|
| 1 | Vein |
| Rank | Characteristic |
|---|---|
| 1 | Vein |
Date: Sep 12, 2014
Geologist: Mark Puumala
Notes: The 7Z amethyst occurrence was visited on September 12, 2014 with the current claim holders, B. Clemons and S. Gurney. The geological description of the occurrence attached to this MDI record is based on observations made during this site visit.
Article - MacGregor Township, District of Thunder Bay
Publication Number: MP119.008 Page: 46-48 Date: 1997
Author: Scott J.F.
Publisher Name: Ontario Geological Survey
Location:
Map - Geological series, Precambrian geology, MacGregor Township, east half, District of Thunder Bay
Publication Number: P2985 Scale: 1:15,840 Date: 1986
Author: Scott J.F., Sequin J.M.
Publisher Name: Ontario Geological Survey
Location:
Publication - Fort William and Port Arthur, and Thunder Cape Map-area, Thunder Bay District, Ontario; Geological Survey of Canada, Memoir 167
Publication Number: GSC Memoir 167 Date: 1931
Author: Tanton, T.L.
Publisher Name: Geological Survey of Canada
Location: https://doi.org/10.4095/100799
MonoMap - Geology of MacGregor Township
Publication Number: OFR5719 Date: 1990
Author: Scott J.F.
Publisher Name: Ontario Geological Survey
Location:
Mono - Amethyst in the Thunder Bay Area
Publication Number: OFR5891 Date: 1994
Author: Garland M.I.
Publisher Name: Ontario Geological Survey
Location:
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