Black Diamond South occurrence, Surprise Lake, Atlin Mining Division, British Columbia, Canadai

Regional Level Types
Black Diamond South occurrence	Occurrence
Surprise Lake	Lake
Atlin Mining Division	Division
British Columbia	Province
Canada	Country

The Black Diamond South occurrence is located on the west side of Boulder Creek, which drains into Surprise Lake, about 20 kilometres north-east of Atlin, British Columbia.
There is a brief description of the occurrence and its history, on the British Columbia “Minfile” site, current to 2013; an excerpt is quoted below:
“The showing is located within the southernmost zone of the Mount Leonard Boss, a small stock removed from the main body of the Late Cretaceous Surprise Lake batholith (Surprise Lake Plutonic Suite) which covers approximately 1100 square kilometres east and northeast of Atlin. The stock is composed of a fine to coarse grained quartz monzonite (alaskite) which is occassionally (sic) feldspar porphyritic. The intrusion is often kaolinitized near mineralized quartz veins. The pluton has intruded into mafic volcanic, ultramafic, and sedimentary rocks of the Upper Paleozoic Cache Creek Complex which is exposed about 1 kilometre south of the occurrence.”
“The main vein of the Garnet occurrence is comprised of dark smoky quartz, strikes 030 degrees and dips 60 degrees to the northwest. The vein varies from 2 to 10 metres wide and has been traced for about 80 metres. Light grey, porphyritic felsic dikes occur both in the immediate footwall of the vein and about 16 metres west of the vein. Mineralization comprises patchy and erratic wolframite, ferberite and rare gold. Sulphide mineralization is minor and is composed of pyrite, chalcopyrite, molybdenite, tetrahedrite and galena.”
Additional comments by Giles Peatfield on this and other occurrences in the area:
Black Diamond South is one of several occurrences of tungsten ¬+ tin + molybdenum + base metal mineralization in the region immediately south of, but not necessarily related to, the Adanac molybdenum deposit (“Minfile” No. 104N 052). Others of interest are: Black Diamond Vein (“Minfile” No. 104N 006); Black Diamond North (“Minfile” No. 104N 054) and Silver Diamond (“Minfile” No. 104N 069). It is best to view these together, because the various reports available are not always perfectly clear as to which specific occurrence geological data refer to, and even the names given are not always consistent. As an example, a report (Read, 1957) which “Minfile” lists as referring to the Black Diamond Vein occurrence almost certainly refers to material from Black Diamond South.
Comments by Giles Peatfield on some of the minerals reported from the locality:
A note of caution: Much of the mineralogical information presented comes from three University of British Columbia mineralography course reports – Mountjoy (1955); Read (1957) and Tribe (1964). These reports apparently refer to the same two specimens, but there are some differences in the minerals identified, as will be pointed out. Note that both the Mountjoy and Tribe reports are included in “Minfile” Property File report PF 600017 – this is not a misprint in the reference section. A further note of caution: The assessment report by Kikauka (2002) contains much mineralogical information, but unfortunately it is not possible to assign the references to specific occurrences, and his work is thus not included in the mineral listing.
Acanthite: Keyte (1980) stated that “At the South Zone a quartz vein contains native silver and argentite.”, but gave no further data. I would regard this as tentative.
Anglesite: Mountjoy (1955) identified anglesite in polished section.
Biotite: Reported only by Aspinall (1970), in quartzite.
Bismuthinite: Reported in polished section by Mountjoy (1955) and by Read (1957), in both cases by microscopy and etch tests.
Cassiterite: Reported by Tribe (1964) as an unknown, but a hand-written note by Dr. R. M. Thompson noted that an X-ray analysis suggested a mixture of cassiterite plus some other mineral. Given the regional mineralogy, and the report by Hemsworth (1951) of small amounts of tin in a small “ore” shipment from the occurrence, cassiterite would be possible in the occurrence.
Galenobismutite : Reported by Mountjoy (1955), by Read (1957), and by Tribe (1964) in polished section. In Tribe’s report, a hand-written note by Dr. R. M. Thompson noted that an X-ray analysis suggested a mixture of galenobismutite plus some other mineral.
Gold: Reported by “Minfile” with no specific reference; probably valid given the reported gold grades.
Matildite: Reported only by Read (1957), in polished section; he identified it by microscopy and etch tests, and noted that it “Occurs as exsolution blades along the crystallographic {111} planes in galena in a Widmanstetten-like texture.”
Molybdenite: Reported only by Aspinall (1970), in quartz veins.
Orthoclase: Reported only by Aspinall (1970), as a constituent of alaskite.
Plagioclase: Reported only by Aspinall (1970), as a constituent of alaskite.
Pyrrhotite: Reported only by Aspinall (1970), in quartzite.
Sericite: A map notation in Aspinall (1970) noted sericite and “white mica” in quartz, in old drill core.
Silver: See note above for acanthite.
Tetrahedrite group: Reported by “Minfile”, with no supporting data; should be regarded as tentative for the locality.
Wolframite group: Hemsworth (1951) reported both ferberite and wolframite at this occurrence; other workers in the region refer to “wolframite”, it is likely that the mineral in question is ferberite but this is not proven.

References

Other Databases

Link to British Columbia Minfile:	104N 053

Other Regions, Features and Areas containing this locality