Alberta Inventors and Inventions - Gibbon's Grizzly Screen

James Gibbons’ "grizzly" screen was a mechanical device that helped improve the return for gold miners working the gravel deposits on the North Saskatchewan River in the 1860s.

Though he never claimed a patent for the grizzly; Gibbons made his claim to the invention in 1922 when the Edmonton Bulletin reported that another man was intending to patent the device. In a 1922 memoir dictated to his friend William Griesbach, Gibbons claimed to have invented the grizzly in 1868. The Bulletin readily gave credit to Gibbons for the invention: "It was an invention adapted to the special circumstances of a special case, and Mr. Gibbons is entitled to every credit for having been the first to give effect to the idea."

In the 1860s, gold mining on gravel deposits was hard, heavy work; miners were required to shovel tonnes of gravel to recover the tiny flakes of gold mixed in with the coarser rock. Panning and washing the gravel was tedious work, and long hours of toil for meagre pay discouraged many of them.

"The idea which finds shape in the "grizzly" is that a maximum amount of gravel and sand can be worked over with a minimum amount of labour," the Edmonton Bulletin noted in 1922.

The invention worked as a component of a three-part system, along with a dump box and sluice box. The screen itself was described in the Bulletin as "made of two end boards of triangular shape connected by iron rods along two sides so that a grating is formed on two of the sides of the triangle."

The grizzly screen was set between the dump box and the sluice box; when water was poured over the gravel in the dump box’s sloped bottom, the gravel flowed over the screen, and the larger rocks were trapped in the screen and dumped to the side, while smaller pebbles, sand and gold flakes fell through to the sluice box, where further processing helped separate the gold.

This was a significantly different system than the "rockers" which used a rocking motion to break apart the gold-bearing clay layers usually found in underground deposits.

The grizzly screen helped the miners recover around $16 a day from the North Saskatchewan gravel flats; however, the season was too short for many to make a living mining gold.

The "grizzly" screen idea has since been updated and modified for use in many mining and metal processing operations to help separate differentially sized particles.

Gold Mining Grizzly