The Mount Meager pumice occurrence covers the area surrounding the confluence of Salal Creek with the Lillooet River, 5 kilometres southwest of Mount Athelstan and northwest of Pemberton.
Volcanics of the Garibaldi Group were first discovered and mapped in 1911. The pumice deposits were first held as a minerals lease by J. MacIsaac. After J. MacIsaac's death in the late 1970s a new lease was issued to W.H. Willes, who explored and exploited the deposit from the mid 1970s to the mid 1980s. The mined pumice was crushed, screened and stockpiled near Pemberton. The operation ceased when an access bridge was washed out. In 1988, L.C. Bustin staked the deposit. The property was purchased by D.R. Carefoot from owners M. Beaupre and B. Chore in 1990. The 1991-1992 program on the property consisted of evaluation for: 1) constructions material (block testing for absorption, compressive strength, density and permeability), 2) stonewash feed and 3) oil absorption.
The pumice, of the Pliocene to Recent Garibaldi Group, outcrops over a length of 2000 metres and is up to 1000 metres wide. Diamond drilling indicates the deposit is up to at least 300 metres thick. The pumice deposit is a volcanic ejecta. The vent is assumed to have been within the Lillooet Valley on the north side of Plinth Peak, with depositional distribution along a northeast plume axis of about 63 degrees, defined by distal and proximal deposits of the Mount Meager volcanic complex. The pumice deposit forms part of the Bridge River ash unit of the Mount Meager volcanic complex. Significant deposits occur on the west facing slopes and valleys along the Lillooet River. The Bridge River ash is described as a crudely stratified breccia with ash deposits up to 20 metres thick. Over 90 per cent of the fragments are cream weathering, porphyritic (hornblende, plagioclase and pyroxene) dacite pumice. The fragments range in maximum size from 10 centimetres to 4 metres.
At the Mount Meager occurrence, the pumice is yellowish grey, weathering to creamy white. It has a density of 860 kilograms per cubic metre. The pumice consists of coarse textured ellipsoidal fragments ranging from 25 to 150 millimetres diameter. The deposit is a well sorted rhyodacitic pumice composed of plagioclase phenocrysts in a frothy cellular groundmass. Black hornblende and biotite flecks are present in minor amounts. The pumice was deposited on a steep paleoslope of bedrock covered by sandy clay tills. The pumice deposit has been partially covered by lahar, slides and/or a thin soil veneer. Internal stratification consists of a band of finer pumice. 0.5 to 1.5 millimetres diameter, approximately 2.6 metres below the upper depositional surface.
In 1992, construction material evaluation was conducted by B.H. Levelton & Associates. Their report concluded that the quality and performance of the pumice was similar to Bend, Oregon pumice (Assessment Report 22669). The results of stonewash testing in 1992 is as follows:
Moisture Content 0.1 %
Abrasion Loss 31.3 %
Apparent Density 0.77 g/cm3
Absorption Capacity 21.2 %
Saturated Density 0.98 g/cm3
Surface Coloration light grey (< 5% FeO)
The results were summarized as marginal for stone-washing and average for acid-washing (Assessment Report 22669, Appendix III). The results of whole rock geochemical analysis are as follows:
Al2O3 15.27 % Ba 720 ppm
CaO 3.26 % Nb 10 ppm
Fe2O3 3.37 % Rb 55 ppm
K2O 2.55 % Sr 480 ppm
MgO 1.31 % Y 30 ppm
Na2O 4.59 % Zr 120 ppm
P2O5 0.18 % Co 3 ppm
SiO2 67.16 % Cu 35 ppm
TiO2 0.48 % Ni 6 ppm
LOI 2.75 %
TOTAL 101.00 %
+H2O 3.40 %
-H2O 0.23 %
(Assessment Report 22669, Petrographic and Sampling Report). The results of oil absorption testing indicate a 1.5 pumice-to-oil ratio by volume (Assessment Report 22669). The pumice appears to have a commercial application, primarily as concrete aggregate used in the manufacture of light-weight concrete and concrete blocks. A secondary application is for the stone-wash of denim clothing (Assessment Report 22669).
Due to delays in permitting and the lateness in the season, Great Pacific Pumice Inc. postponed its production of pumice until June 1996. The property has possible reserves of 5 to 20 million tonnes. A 20-year mine and reclamation plan has been approved and a Mine Development Certificate granted in the spring of 1995 (Information Circular 1996-1, page 20).
In 1998, Great Pacific extracted between 7000 and 8000 cubic metres of pumice. Most of the product goes to horticulture suppliers. There is also potential for pumice as a light weight aggregate filler in the construction industry. Mt. Meager Pumice Products Ltd. supplies Canadian Pumice Stones to a variety of clients.
In 2009, Great Pacific Pumice Ltd. had a forecast production of 3000 m3.