Solution:
The main constituents of pearls are Calcium Carbonate and Magnesium Carbonate.

Solution:
One Joule is equal to 107 ergs.

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The gases used in different types of welding would include Oxygen and Acetylene.

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In fireworks, the green flame is produced because of barium.

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Paper is a thin sheet material produced by mechanically and/or chemically processing cellulose fibres derived from wood, rags, grasses or other vegetable sources in water, draining the water through fine mesh leaving the fibre evenly distributed on the surface, followed by pressing and drying.

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The chromosphere (literally, "sphere of colour') is the second of the three main layers in the Sun's atmosphere and is roughly 2,000 kilometers deep. It sits just above the photosphere and just below the solar transition region. Helium, the lighter of the noble gases, was the first to be discovered. In fact, this element was first identified in the Sun's chromosphere rather than in the Earth.

Solution:
Thorium radioactive pollutant has recently drawn attention of public due to its occurrence in the building material. Thorium is a naturally-occurring, slightly radioactive metal discovered in 1828 by the Swedish chemist Jons Jakob Berzelius, who named it after Thor, the Norse god of thunder. It is found in small amounts in most rocks and soils, where it is about three times more abundant than uranium. The alpha particles can travel only very short distances through most materials and cannot go through human skin.