The Lumby deposit is located about 13 kilometres east of Lumby, north of Blue Springs Creek.
In 1970-1971, two trenches, two pits, a radiometric survey and a ultraviolet lamp survey were completed on the property by Able Explorations Ltd. In 1987, geological mapping and sampling were completed by Brenda Mines Ltd. In 1988, rock sampling and geochemical surveys were done and in 1989, geological and geochemical surveys, diamond drilling, roadwork and metallurgical testing were completed.
A 1.35 by 2.65 kilometre stock of pegmatite intrudes quartz mica schist of the Proterozoic-Paleozoic Kootenay Assemblage and is bounded on the south and west by Eocene Kamloops Group volcanic rocks. Four distinct rock types are recognized in the area and these are: pegmatite, quartz diorite, quartz mica schist and limestone.
The principal pegmatite body of the deposit outcrops in an area 0.75 by 1.5 kilometres. The pegmatite crops out as topographic highs, appears fresh, massive and most often white, but ranges from cream through yellow to reddish orange where stained by iron leached from mica. The pegmatite is frequently in contact with quartz diorite. Typically, the pegmatite consists of 70 to 75 per cent feldspar, 20 to 25 per cent quartz (locally up to 50 per cent), 5 to 7 per cent muscovite and 5 to 15 per cent mafic minerals, commonly biotite, garnet and rarely tourmaline. Locally, regular intergrowths of quartz and feldspar give the pegmatite a graphic texture. Books of biotite and/or muscovite, up to 5 centimetres across, occur sporadically in clusters throughout the pegmatite or as individual flakes. The two micas form 5 per cent of total volume, but are seldom found together. Red to purple garnet (1 to 3 millimetres) occurs in pockets and constitutes 5 to 15 per cent of the rock. In one location only, small (1 to 2 millimetre) crystals of tourmaline were identified. In thin section, iron oxides occur in biotite and along fractures between grains of feldspar and quartz. Feldspar content varies inversely with quartz in distinct zones. A feldspar-rich core zone is flanked by feldspar-poor zones rich in quartz.
Radioactive mineralization occurs in small irregular patches within a large mass of pegmatite enclosed in metamorphic rocks. The local radioactive areas contain erratically dispersed monazite in irregular lensoid masses of fine grained dark, glassy, smoky quartz.
A 5.5 metre long trench in pegmatite exposed a bright yellowish brown glassy mineral, identified as monazite, erratically dispersed along a 0.6 metre wide lens of fine grained, granular, dark, smoky quartz. A chip sample along the length of the trench gave the following chemical compositions: 0.069 per cent thorium oxide, 0.037 per cent uranium, 0.25 per cent yttrium, 0.03 per cent ytterbium, 0.044 per cent lanthanum, 0.07 per cent cerium, 0.046 per cent neodymium, 0.027 per cent erbium, 0.021 per cent gadolinium and 0.003 per cent thulium (Geology, Exploration and Mining in British Columbia 1971). Grab samples analyzed up to 0.20 per cent uranium and a 0.8 metre chip sample assayed 0.13 per cent uranium (Assessment Report 3434). The ratio of thorium to uranium ranged from 6:1 to 12:1. Fluorescent secondary uranium minerals occur within the radioactive zones.
Massive, grey, fine to medium-grained, weakly foliated quartz diorite crops out as a prominent topographic high immediately north of the pegmatite stock. The diorite is cut by thin pegmatite dikes and contains small (less than 1 millimetre) red garnets. South of the intrusion, xenoliths of quartz diorite are incorporated in the pegmatite. These are often tens of metres across and similar in appearance to the more massive diorite to the north, but appear partially digested.
Large (tens of metres across) xenoliths of fine-grained, medium to dark grey quartz mica schist are incorporated in the main pegmatite stock. The schist is foliated, several metres thick, locally intruded by lenses of quartz or pegmatite and often sheared. Small (1 to 3 millimetres) red to purple garnets are common.
Medium to dark grey, fine-grained crystalline limestone occurs as inclusions in the pegmatite stock. The limestone is also found within beds of quartz mica schist and contains stringers of quartz or pegmatite. Small scale isoclinal folds and boudinage structures are prominent features in the limestone.
One representative sample of the pegmatite was sent to CANMET for processing. The non-magnetic feldspar concentrate was analyzed with the following results:
Low iron content and acceptable potassium and alumina content indicate that the Lumby pegmatite has good potential to produce a high-quality potash feldspar with liberation of 20 mesh (Exploration in British Columbia 1987).
Indicated (probable) reserves are 100 million tonnes of material grading 50 per cent feldspar, 18 per cent SiO2 and 3 per cent mica (Open File 1992-1).