The Eng 3 occurrence is located on the western flank of Mount Shiziko near a tributary of Terrahina Creek (Weir Creek) called Feather Creek, about 42 kilometres east of the community of Atlin.

The showing area is underlain by the Surprise Lake batholith (Surprise Lake Plutonic Suite) which covers about 1100 square kilometres east and northeast of Atlin. The batholith is dated at 70.6 plus or minus 3.8 million years or Late Cretaceous (Map 52). It is composed primarily of medium grained, equigranular alaskite which is essentially a leucocratic granite with microcline and orthoclase with subordinate quartz, and may or may not contain plagioclase and mafics. There are some coarse grained, quartz feldspar porphyritic varieties. The contacts between the various textural varieties are commonly gradational. Massive aplitic dikes crosscut the batholith. Very coarse grained pegmatitic zones also occur within the alaskite containing large quartz and feldspar crystals and books of biotite. The width of these zones varies considerably, but the contacts are almost always sharp.

At the Eng 3 showing, a magnetite vein, up to 5 metres wide, cuts the alaskite and contains up to 0.55 per cent zinc and 0.1 per cent lead in the form of sphalerite and galena (Assessment Report 8413). Mineralized boulders rich in sphalerite and cassiterite have been found nearby and on strike with the vein.

In 1977, eleven CY and Eng claims were staked in the Weir Mountain area for Mattagami Lake Mines Ltd. to cover a radioactive area discovered by a regional helicopter-borne radiometric survey. Geochemical sampling, radon detection in water and soil, and radiometric surveys were carried out to cover most of the CY claims in 1977. Detailed geochemical and geophysical surveys (magnetometer, Radem, VLF-EM, induced polarization, radiometric) were completed during the summer of 1978, predominantly on the CY-3, CY-4 and CY-6 claims. During the first part of the 1979 program (June and July) work was concentrated on the CY-3, CY-6 to CY-9, and ENG 1-3 claims. This included geological mapping, prospecting, magnetometer and radiometric surveying, and radon in soil surveys. This work was conducted on four interconnected grids; magnetometer surveys were conducted over all grids although the survey is not complete in some areas. More than 640 soil samples were collected over three of the grids.