January 2010 – Siderite
The name mica is thought to derive from the Latin word, micare – “to glitter”. This no doubt refers to the brilliant sparkle when light is reflected and refracted by this mineral.
More correctly, the Mica...
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October – Mica
The name mica is thought to derive from the Latin word, micare – “to glitter”. This no doubt refers to the brilliant sparkle when light is reflected and refracted by this mineral.
More correctly, the Mica Group of minerals are sheet silicates. This means that instead of growing as a large crystal they form in lots of very thin layers. The minerals are often transparent and in the past were used as a substitute for glass. It is a widely distributed mineral occurring in igneous, metamorphic, and sedimentary rocks and can form the planet’s largest-known crystals reaching several tens of metres in length, particularly within granitic pegmatites.
China is the greatest world producer of mica, with the largest deposits being found on the Indian sub-continent, USA, South Korea, and Canada. The mineral has multifarious uses including within Geiger-Müller Tubes, heating elements, capacitors, refractory windows (isinglass), in toothpaste, and adds a bright shimmer to make-up.
Throughout the ages, fine powders of mica have been used for various purposes, including decorative purposes. The coloured body paints used by Hindus of North India during holi festival contain fine small crystals of mica. The majestic Padmanabhapuram palace, 65 km (40 miles) from Trivandrum in India, has colored mica windows.
Mica occurs in the Tees Valley most commonly as small specks within the Jurassic sedimentary strata and is generally indicative of the sediment being deposited in quiet water conditions.