Likely created in Austria, Belgium, Germany or France, not sure because of the absence of hallmarks, which were not uncommon. The design Source of inspiration was Christianity. The pendent was made by the lost wax method of Jewelry design, this method goes back to the middle ages, this cross was made by a master goldsmith.  
The pendant is circa 1750, George II, Early Georgian time period.
The filigree frills of this 22K yellow gold cross are made with great detail. The designed is called "Croix "à la Jeanette" which translates to "Gold Cross".
Style: Rococo - Rococo (less commonly roccoco) also referred to as "Late Baroque" is an 18th century style which developed as Baroque artists gave up their symmetry and became increasingly more ornate, florid, and playful. Rococo rooms were designed as total works of art with elegant and ornate furniture, small sculptures, ornamental mirrors, jewelry and tapestry complementing architecture, reliefs, and wall paintings. It was largely supplanted by the neoclassic style. In 1835 the Dictionary of the French Academy stated that the word Rococo "usually covers the kind of ornament, style and design associated with Louis XV's reign and the beginning of that of Louis XVI". It includes therefore, all types of art produced around the middle of the 18th century in France. Style specifics: Rococo is a style of decoration that followed, c.1730, the baroque style in France (where it was also called rocaille), the principal features of which are asymmetry of ornament and a repertoire consisting to a considerable extent of shells, flowers, foliage, and scrollwork. It was developed in France under Louis XV, 1715-74, and spread to Italy, Germany, and Austria and to a lesser extent to England. 
The pendant is set with six table cut diamonds, which are conical wrap set. 10 small triangular point-cut diamonds and 8 flower set, rose cut diamonds.
History of Diamond Cuts & Antique Diamond Cuts:
Diamond cutting has a history of over 700 years (Since the middle ages). However prior to this diamonds were enjoyed in their natural octahedral state. Poorly formed, less symmetrical diamonds were not used in jewelry.
Since ancient times, craftsmen have tried to improve its beauty. At first it seemed like an impossible task, because it was so hard that conventional cutting tools could not be used to cut them. Progress was made only after discovering that a diamond could cut another diamond.
Polishing of the natural octahedral crystal to create unblemished facets was the first form of improvement. The first gem cutting machines were available during the 1300's. A diamond cutter/ polisher is known as a “diamantaire".

Point Cut Diamond
The Point Cut was among the earliest types of diamond cuts during the early 1300's. It was shaped according to the natural octagonal diamond crystal. The point cut was later improved by cutting part of the upper half of a point cut diamond to give the 'Table Cut Diamond' The table cut was popular during the mid 15th Century.

The pendant has a re-placed bail, the original one may have worn through. There is a 20-inch, 14 carat gold chain added to the pendant. The size is 3 1/4 inches tall and 1 5/8 across, and is in excellent condition. This cross is a one of a kind work of art, magnificently created and would be exquisite to wear.