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File Created: 24-Jul-1985 by BC Geological Survey (BCGS)
Last Edit:  02-Dec-2010 by Laura deGroot (LDG)

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NMI 092I13 Bnt1
BCGS Map 092I072
Status Producer NTS Map 092I13E
Latitude 050º 46' 17'' UTM 10 (NAD 83)
Longitude 121º 37' 02'' Northing 5625314
Easting 597503
Commodities Bentonite, Coal Deposit Types E06 : Bentonite
Tectonic Belt Intermontane Terrane Overlap Assemblage
Capsule Geology

This bentonite prospect is located in the Hat Creek Valley, 20 kilometres west-southwest of the community of Cache Creek.

Hat Creek is underlain by a north trending, fault bounded trough containing over 1000 metres of clastic sediments of the Eocene Hat Creek Formation (Princeton Group) overlain by 400 to 600 metres of felsic to intermediate volcanics of the Eocene Kamloops Group. The Hat Creek Formation consists of a lower unit of coal with intercalations of siltstone, conglomerate and sandstone overlain by an upper unit of siltstone and claystone up to 600 metres thick. Bentonite is widely distributed within both the coal and the siltstone-claystone sequence. The basin is warped into two northerly plunging synclines and an intervening faulted anticline preserved within a northerly trending system of easterly dipping reverse and strike-slip faults.

A zone of bentonitic clay and sandstone, up to 100 metres thick, overlain by coal and underlain by conglomerate, outcrops along the nose of a subsidiary southward plunging syncline and contains zones of clean bentonite, several metres in thickness (N. Skermer, personal communication, 1991). Near surface, the bentonite is brown and oxidized. The unoxidized bentonite below is blue in colour and displays more desirable swelling properties. On surface, bentonite occurs in siltstone and minor shale intercalations at the south end of a partly slumped, 9-metre deep bulldozer trench. An x-ray diffractogram of this material shows that it consists mostly of montmorillonite and feldspar. Exchangeable cation analyses and cation exchange capacity of this uncontaminated surface sample show that it contains mainly divalent exchangeable cations (Table).



Exchangeable Ca, Na, K and Mg Analyses

and Cation Exchange Capacity (CEC)*

Exchangeable Cation Analysis


Unit/ Loc. (mequiv./100g) (mequiv./100g)

Sample #' Mg Ca K Na Total

Hat Creek Member

C86-439A B1 10.6 18.3 1.6 14.7 45.4 46.8

' B = Bentonite

* Analysed samples weigh 10-15 grams and are crushed to -120 mesh.


Other samples of bentonite are reported to contain excess amounts of cristobalite (N. Skermer, personal communication, 1991).

Significant bentonite-bearing sections were first noted by Pacific Bentonite Ltd. in a hole drilled by B.C. Hydro and Power Authority (DDH 76-802). The deposit was auger-drilled in 1989 and 1990 by Pacific Bentonite to search for extensions of bentonitic horizons discovered during development of the Hat Creek coal deposit by B.C. Hydro. Inferred (possible) reserves are 30 million tonnes of bentonite (Open File 1992-1).

Pacific Bentonite Ltd. proposed to mine 10,000 tonnes of bentonite in 1995.

Lafarge purchased about 7000 tonnes of alumina-rich burnt shale from Pacific Bentonite Ltd for use in cement-making. The material was mined under a bulk sample permit at the Decor pit (formerly called Ben or Hat Creek). Late in 2004, Pacific Bentonite applied for a mine lease and a 35 000 to 50 000 tonne per year quarry permit, and expects that larger quantities can be supplied to Lafarge in the coming years. Once the quarry permit is in place, the company intends to further develop landscaping and decorative markets for the shale. In addition, the property hosts a large bentonite deposit which is being investigated for municipal engineering and tile manufacture applications.

EMPR ASS RPT 20358, 22547, 23562, 24854, 25404
EMPR EXPL *2004-55
EMPR FIELDWORK 1975, pp. 104-115; 1979, pp. 97-99; 1980, pp. 73-78;
1981, pp. 270,271; *1986, pp. 253, 254
EMPR GEOLOGY 1975, pp. 99-118
EMPR INF CIRC 1991-1, pp. 18,61
EMPR OF 1987-18; 1988-29; *1990-23; 1992-1; 1992-9; 1996-1, p. 20
EMPR PF (B.C. Hydro and Power Authority, Environmental Studies
Report, May 1978)
GSC MAP 1010A; 1386A; 42-1989
GSC OF 165; 866; 980
GSC P 46-8; 47-10; 73-1A, p. 212; 74-49; 81-1A, pp. 185-189,217-221;
82-1A, pp. 293-297; 85-1A, pp. 349-358
GSC SUM RPT 1925 Part A, pp. 164-181