The mica group of sheet silicate (phyllosilicate) minerals includes several closely related materials having nearly perfect basal cleavage. All are monoclinic, with a tendency towards pseudohexagonal crystals, and are similar in chemical composition. The nearly perfect cleavage, which is the most prominent characteristic of mica, is explained by the hexagonal sheet-like arrangement of its atoms
The word mica is derived from the Latin word mica, meaning a crumb, and probably influenced by micare, to glitter.
Mica is widely distributed and occurs in igneous, metamorphic and sedimentary regimes. Large crystals of mica used for various applications are typically mined from granitic pegmatites.
The largest documented single crystal of mica (phlogopite) was found in Lacey Mine, Ontario, Canada. It measured 10 × 4.3 × 4.3 m and weighed about 330 tonnes. Similar-sized crystals were also found in Karelia, Russia.
Sheet mica is used in electrical components, electronics, isinglass, and atomic force microscopy. Other uses include diaphragms for oxygen-breathing equipment, marker dials for navigation compasses, optical filters, pyrometers, thermal regulators, stove and kerosene heater windows, radiation aperture covers for microwave ovens, and micathermic heater elements.
In the early 1940's Justin Purdy and his partner Huntley McDonald began a small operation and explored further finding other excellent outcroppings among the granite terrain. Justin Purdy took a few loads to dealers and began to make some money. In 1941 he died in a truck crash and the property went back to his father who soon sold it to larger concerns and production accelerated. Bill Steer notes that in the 2 active production intervals 1941-1945 and 1949-53 three million pounds of mica were mined at a value of $1,577,000.
During peak periods upwards of 50 men were employed at the mine and worked 6 days a week. Dozens of women worked in the sorting plant in Mattawa and later in a second plant in North Bay. The mica was taken from the mine
to the CPR station in Eau Claire for shipping. The mine had its own bunk house, dining room, office, etc.
Several pieces of mica were of museum quality and brought high prices. Mattawa mica is on display in New York, the royal Ontario Museum and the Mattawa Museum. John Laframboise, a miner who worked at the mattawan site is featured as a part of the display. He identified the people in the photo of the mine shown here.
In order to claim this find you have to send us answers on following questions:
- At the posted coordinates you will find a lot of mica pieces stuck in the rocks. In what mineral mica pieces are stuck?
- What colors of mica you can find in the area?
- How thin are the mica sheets? Can you see through them?
- At the right from the main entrance to the mine you can view a big crack. When you go to the crack area on both sides of the rocks you can find sample drilling holes. How many holes you can find on each side?