Antique Edwadian Onyx and Ormolu Floor Standard Lamp circa 1900

Ormolu - (from French 'or moulu', signifying ground or pounded gold) is an 18th-century English term for applying finely ground, high-carat gold in a mercury amalgam to an object of bronze.The mercury is driven off in a kiln leaving behind a gold-coloured veneer known as 'gilt bronze'.

The manufacture of true ormolu employs a process known as mercury-gilding or fire-gilding, in which a solution of nitrate of mercury is applied to a piece of copper, brass, or bronze, followed by the application of an amalgam of gold and mercury. The item was then exposed to extreme heat until the mercury burned off and the gold remained, adhered to the metal object.

No true ormolu was produced in France after around 1830 because legislation had outlawed the use of mercury. Therefore, other techniques were used instead but nothing surpasses the original mercury-firing ormolu method for sheer beauty and richness of colour. Electroplating is the most common modern technique. Ormolu techniques are essentially the same as those used on silver, to produce silver-gilt (also known as vermeil).

Onyx is a gemstone whose description can have several connotations. Its most accepted gemstone definition describes a solid black Chalcedony or a banded or layered black and white Chalcedony. The term Onyx is occasionally used to described any engraved stone with a solid color base, or it may describe any banded gemstone with parallel banding. In its solid black form, Onyx is the most traditional black gemstone.

Onyx is an ancient gemstone, having been used in jewelry and as an ornamental gemstone for carvings since antiquity. Onyx has traditionally been one of the most important engraving and cameo gemstones, where its most common form was a black base with a white upper layer. Although still used a minor gemstone today, the significance and value of Onyx has been diminished as compared to ancient times. 

When Onyx is banded black and white, it can be jointly classified as both Agate and Onyx. However, many require Onyx to have banding in roughly parallel lines, whereas other forms of Agate can have wavy or concentric forms of banding.