Diamonds may well be a girl's best friend and may men may also consider wearing diamonds, but for sheer volume of trade, for more coloured stones are sold. This is because the colours of most precious and semi-precious stones have always attracted the greatest attention. Rubies and emeralds as well as blue and yellow sapphires are sought after rather than clear white zircons or light coloured topaz. The reasons for this arise from the profound interaction of colour with human moods and behaviour.
To begin with,the sun radiates many colours. When the sun goes behind the black clouds of the monsoon or is less visible during the long winter of northen latitudes, a profound depression settle on all living beings. Bears hinbernate and birds migrate to sunnier climates. Social scientists aver than even the human psyche is affected. Sunlight appears to alleviate almost every affliction and chronic disease. Once recommended as a cure for tuberculosis, solar radiation improves digestion and nutrition, quickens blood and lymph circulation and increases the elimination of impurities through the skin. when light enters the body (through the eyes of the skin) it generates signals that travel through the nerves to the pineal gland attached to the brain. In turn this controls our daily physio-biological rhythms. The gland responds to light levels by producing melatonin that determines metabolic rhythm.