In the most general sense, deposits in the District are orogenic, polymetallic veins with lesser disseminated mineralization emanating from the principal veins.

The Bunker Hill Mine workings extend 8,600 feet along strike of the overturned beds of the Upper Revett formation that host the mineralization, extending 7,000 feet downdip parallel to the axial plane of the plunging anticline, covering 5,200 vertical feet from ~3,500 ft msl to -1,700 ft msl. More than 30 individually named deposits were mined historically in separate stopes, with two distinct types of deposits exploited: tabular Bluebird (BB) zones that parallel bedding and are associated with the fold structures, and later Galena-Quartz (GQ) Veins cutting through bedding with sharp walls. The Bluebird Deposits, such as the March, have been mined for up to 1,400 ft along strike, 4,000 ft downdip, covering 2,400 ft in elevation, with thicknesses of the generally tabular zones up to 150 ft. GalenaQuartz Veins were historically mined along strike lengths of up to 800 ft, and downdip up to 3,700 ft, with mined thicknesses from 5-15 ft.

Mineralization at Bunker Hill falls in four categories, described below from oldest to youngest events:

- Bluebird Veins (“BB”): W--NW striking, SW-dipping, variable ratio of sphalerite-pyrite-siderite mineralization. Thick, tabular cores with gradational margins bleeding out along bedding and fractures;

- Stringer/Disseminated Zones: Disseminat ........

Long-hole stoping with fill (LHOS), cut-and-fill and possibly room-and-pillar mining with fill are the only methods viable for sustained operations today. LHOS is the preferred mining method with limited cut-and-fill mining at Bunker HIll. Room-and-pillar mining is not in the current plan.

LONG-HOLE OPEN STOPING WITH HYDRAULIC FILL
Long-hole open stoping (LHOS) is employed with engineered hydraulic fill. Long-hole panels are established by driving a top cut and bottom cut into the mineralized zone leaving a bench between the upper and lower cuts. This bench is then extracted utilizing the top cut as drilling and loading access and the lower cut for mucking access. LHOS are typically mucked with remote control equipment for safety. Stope centerlines are laid out and designated as alternating primary and secondary excavations. The primary stopes are taken first with native rock on all sides. As they are mined-out, they are filled with an engineered hydraulic backfill. The secondary stopes are then mined out adjacent to the primary backfill. The fill strength requirements for secondary stopes are typically much less as they are the last excavations taken in an area. Secondary stopes are typically filled with development material and low or zero cement content hydraulic fill. LHOS represents over 97% of the reserve tons. Planned dilution is included in the stope shapes and defined as M & I material below the cut-off value. External dilution is included at 5% for ........

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