The oyster is then returned to the water and in time covers the bead with layers of nacre, the pearl substance. At the end of the prescribed period, the oysters are taken out and the pearls removed. It's a magnifying piece, normally 10-power, worn by the jeweler over one eye, enabling him to see the minute details necessary for careful and thorough examination. This is know as gold smudge. The most common reason is metallic abrasion, caused by makeup on skin and clothing.
Cosmetics often contain compounds harder than jewelry itself, which wear or rub off tiny particles.
Very fine metal appears black rather than metallic. When this dust comes into contact with skin, it sticks, forming a black smudge. Another cause is actual corrosion of the non-gold alloys, silver or copper which is mixed into the gold. Perspiration and smog fumes attach these metals and are evident as tarnish that rubs off on the skin. A suggestion is to remove jewelry often and use absorbent powder, free of abrasives on skin that comes in contact with jewelry.