Silver Crater Mine, previously known as the Basin Deposit,
is an abandoned mine in
Cardiff, Ontario. It has produced some of the world's most notable
betafite
Betafite is a mineral group in the pyrochlore supergroup, with the chemical formula . Betafite typically occurs as a primary mineral in granite pegmatites, rarely in carbonatites. Originally defined by the B-site atom Ti, the development of new ...
crystals.
The mine has been worked since the late 19th-century, with industrial mining of
mica
Micas ( ) are a group of silicate minerals whose outstanding physical characteristic is that individual mica crystals can easily be split into extremely thin elastic plates. This characteristic is described as perfect basal cleavage. Mica is ...
starting in 1927. Uranium was sought in the 1950s and the mine has been abandoned since 1955.
Location, nomenclature, and geology
Silver Crater mine is located 8 miles west of
Bancroft.
It was previously known as the Basin Deposit or Basic Occurrence.
The mine is located in the
Grenville Province
The Grenville Province is a tectonically complex region, in Eastern Canada, that contains many different aged accreted terranes from various origins. It exists southeast of the Grenville Front and extends from Labrador southwestern to Lake Huron. ...
geological area.
Mining activity enabled access to
crustal carbonatite
Carbonatite () is a type of intrusive rock, intrusive or extrusive rock, extrusive igneous rock defined by mineralogic composition consisting of greater than 50% carbonate minerals. Carbonatites may be confused with marble and may require geoche ...
in a
biotite
Biotite is a common group of phyllosilicate minerals within the mica group, with the approximate chemical formula . It is primarily a solid-solution series between the iron-endmember annite, and the magnesium-endmember phlogopite; more alumino ...
-
amphibolite
Amphibolite () is a metamorphic rock that contains amphibole, especially hornblende and actinolite, as well as plagioclase feldspar, but with little or no quartz. It is typically dark-colored and dense, with a weakly foliated or schistose (flaky ...
and syenitized
gneiss
Gneiss ( ) is a common and widely distributed type of metamorphic rock. It is formed by high-temperature and high-pressure metamorphic processes acting on formations composed of igneous or sedimentary rocks. Gneiss forms at higher temperatures an ...
rock, located between an area of granite to the north and marble to the south.
Geologists assess that the minerals found at the mine reached the current location about 1,050 or about 1,150 million years ago.
History and activities
Prospectors have worked the area of the mine since the late 19th-century, seeking
mica
Micas ( ) are a group of silicate minerals whose outstanding physical characteristic is that individual mica crystals can easily be split into extremely thin elastic plates. This characteristic is described as perfect basal cleavage. Mica is ...
,
phosphate
In chemistry, a phosphate is an anion, salt, functional group or ester derived from a phosphoric acid. It most commonly means orthophosphate, a derivative of orthophosphoric acid .
The phosphate or orthophosphate ion is derived from phospho ...
, and
feldspar
Feldspars are a group of rock-forming aluminium tectosilicate minerals, also containing other cations such as sodium, calcium, potassium, or barium. The most common members of the feldspar group are the ''plagioclase'' (sodium-calcium) feldsp ...
.
S. Orser and D. J. Wilson worked the mine in 1925. In 1927, Bancroft Mining Company started excavations and found a cavity holding
albite
Albite is a plagioclase feldspar mineral. It is the sodium endmember of the plagioclase solid solution series. It represents a plagioclase with less than 10% anorthite content. The pure albite endmember has the formula . It is a tectosilicate. I ...
,
fluorite
Fluorite (also called fluorspar) is the mineral form of calcium fluoride, CaF2. It belongs to the halide minerals. It crystallizes in isometric cubic habit, although octahedral and more complex isometric forms are not uncommon.
The Mohs sca ...
,
pyrite
The mineral pyrite (), or iron pyrite, also known as fool's gold, is an iron sulfide with the chemical formula Iron, FeSulfur, S2 (iron (II) disulfide). Pyrite is the most abundant sulfide mineral.
Pyrite's metallic Luster (mineralogy), lust ...
,
sphene
Titanite, or sphene (from the Greek ''sphenos'' (σφηνώ), meaning wedge), is a calcium titanium nesosilicate mineral, Ca Ti Si O5. Trace impurities of iron and aluminium are typically present. Also commonly present are rare earth metals in ...
, and
apatite
Apatite is a group of phosphate minerals, usually hydroxyapatite, fluorapatite and chlorapatite, with high concentrations of OH−, F− and Cl− ions, respectively, in the crystal. The formula of the admixture of the three most common e ...
crystals on the cavity floor.
Pits were dug around the mine from which mica crystals as large as four-feet across were harvested until the 1940s.
Between the mica formatings,
apatite
Apatite is a group of phosphate minerals, usually hydroxyapatite, fluorapatite and chlorapatite, with high concentrations of OH−, F− and Cl− ions, respectively, in the crystal. The formula of the admixture of the three most common e ...
,
betafite
Betafite is a mineral group in the pyrochlore supergroup, with the chemical formula . Betafite typically occurs as a primary mineral in granite pegmatites, rarely in carbonatites. Originally defined by the B-site atom Ti, the development of new ...
, and
lepidomelane were also found.
Bancroft Mica and Stone Products Mining Syndicate operated the mine from 1947 to 1949 and sold the mica which they extracted from a 30 foot by 65 foot wide open pit.
[J. Satterly and D. F. Hewitt, ]
Some Radioactive Mineral Occurrence in the Bancroft Area
'', Province on Ontario, 1955
Toronto-based Silver Crater Mines incorporated in 1951,
bought the mine in 1953,
and operated it from 1953 to 1955, hoping to find uranium, and driving a 70-metre deep
adit
An adit (from Latin ''aditus'', entrance) is an entrance to an underground mine which is horizontal or nearly horizontal, by which the mine can be entered, drained of water, ventilated, and minerals extracted at the lowest convenient level. Adits ...
into the hillside.
Silver Crater Mines is a subsidiary of the International Cobalt and Silver Mining Company
(incorporated September 19, 1906,
Sault Ste. Marie
Sault Ste. Marie is a cross-border region of Canada and the United States located on St. Marys River, which drains Lake Superior into Lake Huron. Founded as a single settlement in 1668, Sault Ste. Marie was divided in 1817 by the establishment of ...
) Mining activity ceased in 1955.
Over the years, the mine has produced world class crystals of titanite, apatite, mica, and zircon.
Silver Crater Mine is most noted for its unusual
betafite
Betafite is a mineral group in the pyrochlore supergroup, with the chemical formula . Betafite typically occurs as a primary mineral in granite pegmatites, rarely in carbonatites. Originally defined by the B-site atom Ti, the development of new ...
crystals, which geologists have yet to sufficiently analyse to understand their geological origins. Betafite crystals from the mine contain 15% to 20% uranium, making them highly radioactive.
As recently as 2006,
rockhounds visited the mine to collect specimens.
Mineral gallery
See also
*
Uranium mining in the Bancroft area
Uranium mining around Bancroft, Ontario, was conducted at four sites, beginning in the early 1950s and concluding by 1982. Bancroft was one of two major uranium-producing areas in Ontario, and one of seven in Canada, all located along the edge ...
*
Grenville orogeny
The Grenville orogeny was a long-lived Mesoproterozoic mountain-building event associated with the assembly of the supercontinent Rodinia. Its record is a prominent orogenic belt which spans a significant portion of the North American continent, ...
*
List of mines in the Bancroft area
The following are a list of notable mines and quarries within 50 miles of Bancroft, Ontario.
{, class="wikitable"
, +
!Name(s)
!Primary mineral(s)
!Location
!Years active
!Type
!Owner (and parent companies)
, -
, Bicroft Mine
, Uranium
, Cardiff
, ...
References
{{authority control
Underground mines in Canada
Former mines in Ontario
History of Hastings County
History of Canada (1945–1960)
History of mining in Ontario