Ontario Mineral Inventory

Ontario Geological Survey
Permanent Link to this Record: MDI000000001710

Record: MDI000000001710

General

Commodities

Primary Commodities: Amethyst

Secondary Commodities: Mineral Specimen

Location

Township or Area: McTavish

Latitude: 48° 41' 43.29"    Longitude: -88° 39' 45.68"

UTM Zone: 16    Easting: 377649   Northing: 5394925    UTM Datum: NAD83

Resident Geologist District: Thunder Bay South

NTS Grid: 52A10NE

Point Location Description: Pit area

Location Method: Other

Access Description: Turn onto Pearl Road No. 5 from Highway 11/17, then take first left after the railway tracks for 4.5

Exploration History

Interest in amethyst exploration in the Pearl area was sparked by the discovery of large amethyst veins near Elbow Lake in the 1950s during road construction. In the early 1960’s the occurrence was staked and ultimately was developed into the Thunder Bay Amethyst Mine. Additional prospecting activity during the 1960s uncovered numerous additional amethyst showings to the east of the Thunder Bay Amethyst Mine, in the area where the present-day Pearl Lake Amethyst Mine is located. 2003-05: Following an approximately 15 year period of inactivity, W.D. Richardson and D.J. Arseneault carried out a prospecting and overburden stripping/trenching program on the mine property. 2014: W.R. Richardson holds MNR Aggregate Permit No. 607322 which allows for the extraction of up to 5 t/year of material from a 0.47 ha quarry area. Mine name was changed to Bill’s Old Amethyst Mine. 2016: property was transferred to G. Blakely.

Assessment Work on File

Geology

Province: Superior

Geological Age: Archean  

Geology Comments

Jul 27, 2017 (Therese Pettigrew) - The area was mapped by McIlwaine (1971) for the Ontario Geological Surey. The unconformity between the Archean and Proterozoic is exposed in various places on the property. A main fault zone, trending 035 degrees, characterized by a breccia zone 5 to 10 m wide, separated Archean granite to the NW from Sibley Group conglomerate to the SE. A secondary fracture system, trending at 070 to 090 degrees has been dilated by the first fault creating spaces and vugs perfect for amethyst deposition (Garland, 1994).

Lithology

Lithology Comments

Jul 27, 2017 (Therese Pettigrew) - The Archean monzonite is a dark pink, coarse-grained, potassium-rich rock with pegmatitic sections. Areas next to amethyst veins have bleached to a white colour due to kaolinization of the feldspar Metasedimentary xenoliths occur as biotite-chlorite schists within the monzonite. The conglomerate consists of well-rounded cobbles averaging 10 cm, occasionally up to 50 cm in diameter, cemented by a sandy matrix. Granite cobbles predominate. Gunflint taconite and sandstone occur rarely as cobbles near the bottom of the unit and all the cobbles are matrix supported (Garland, 1994).

Mineralization

Mineralization Comments

Jun 10, 2014 (Mark Puumala) - The Pearl Lake Amethyst Mine operates under MNR quarry permit number 607322. The quarry permit covers an area of 0.47 ha and allows for the annual extraction of up to 5 tonnes

Jul 27, 2017 (Therese Pettigrew) - There are 5 areas along the main fault zone which have been worked for amethyst. The northern working consists of a pit blasted into the side of a monzonite knoll. The breccia zone in this pit strikes 070 degrees and is 2 m wide. The fragments are angular pieces of mudstone, monzonite, and gneissic rock in a white quartz matrix. Pink barite occurs next to the wall rocks and coarse amethyst veins occur between the barite and the breccia. The host rock on both sides is Archean monzonite and bleaching of the monzonite is quite evident along the walls. Dark purple amethyst lines vugs within the breccia and as massive vein material along the sides of the breccia. The main fault zone which trends at 035 degrees can be followed to the southwest from the northern pit by tracing a breccia zone exposed along the side of a linear wetland. Sibley Group conglomerate outcrops to the southeast of the breccia Archean monzonite on the northwest side is visible where the wetland narrows to the width of the breccia zone, about 10 m. Amethyst occurs within the breccia in vugs and as veins. There are small pits along the breccia zone where amethyst has been mined. Since amethyst mineralization is fairly continuous in the breccia, it can be mined wherever breccia is exposed. The southern working area, where the wetland narrows and monzonite and conglomerate are exposed, a large, water-filled pit has been blasted into the breccia. In the monzonite hill northwest of this pit, a large, open fracture, 1 m wide, 5 m deep, and surface extension of 5 m, was lined with large, dark purple amethyst crystals. This enormous vug has supplied the mine with many exceptional samples and the bottom of the vug is still clay-filled (Garland, 1994).

Mineral Record Details

References

File - Resident Geologist Mineral Deposit File 52A10NE – Pearl Lake Amethyst

Publication Number: Date:

Author:

Publisher Name:

Location: Thunder Bay RGP office

Mono - Amethyst in the Thunder Bay Area

Publication Number: OFR5891 Page: 142-147  Date: 1994

Author: Garland M.I.

Publisher Name: Ontario Geological Survey

Location:

Map - Geological series, McTavish Township (west part of north half), District of Thunder Bay

Publication Number: P0720 Scale: 1:15,840    Date: 1997

Author: McIlwaine W.H.

Publisher Name: Ontario Dept. of Mines and Northern Affairs

Location:

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For detailed information regarding this mineral record please contact the Thunder Bay South Resident Geologist District Office