Odds ‘n’ Sods — Block carving at Helen

The first “block carving” at the Helen mine of Algoma Steel was in a block of siderite ore measuring 500 ft. long, 250 ft. wide and 300 ft. high. Situated under an open-pit floor, the block contained 3 million tons.

The ore had been severely fractured by a series of linear and traverse fault systems. It lay in an east-west position, with a uniform, southerly dip of 70.

In preparation for mining, service raises were driven through to surface at the four corners, and also midway in the footwall and hangingwall. These were joined by fringe drifts around the perimeter of the block at vertical intervals of 70 ft.

Besides providing access, these raises were used for longhole drilling when cutting loose the block to surface, along the footwall, and when cutting loose the northern half of the western pillar boundary, also to surface. The western half of the block was completely undercut so that sitting beneath the undercut opening were 36 draw points, each with a diameter of 40 ft., ready to receive the caved ore.

The initial cave was set to occur in the extreme northwestern corner of the block; this area was the weakest and farthest from the centre of gravity of the block.

The mine’s siderite has a pleasing, creamy-beige tone and the walls, when seen from a distance underground, suggest clean and subdued looking slabs of alabaster or marble.

Standing in the undercut, with the tops of the draw points arranged in neat rows and with the light colored walls in the distance, one is struck by the quiet stillness of the surroundings. The vast emptiness creates the impression of a pristine environment. These routine excursions to the undercut were eagerly anticipated by operating personnel, creating a quiet air of expectancy.

After three months of patiently waiting, minor clues were uncovered that suggested the block was becoming active. One such clue was the fine, white powder that occasionally fell from the back of the undercut. This indicated that small fractures in the ore were being squeezed and that the block was taking on increased pressure.

At the time, our inspection trips to the undercut were always arranged in safe areas where we could stand unharmed and admire the beauty of the surroundings.

Early one morning, in the fourth month of waiting, there was a loud crack followed by a heavy thump — about 300,000 tons of well-fragmented ore came tumbling down in the designated area.

For a miner to stand at the bottom of this fragmented mass of ore and look up to the opening to surface, 300 ft. above, was an unforgettable experience. Deposits such as the Helen are rare; in fact, there are no other siderite producers in the world.

Underground production costs at the operation, where the mining system was patterned after the Climax mine in Colorado, were allegedly the lowest in Canada.

The mine received visitors from many countries, including Russia and China. And, going back to the First World War, the tradition at Helen has always been co-operation and efficiency.

— The author is a resident of Orillia, Ont.