Gemstones are either mined or found in alluvial deposits. They occur as natural crystals and each species has its own particualr crystal structure. The style of cutting stones has developed over the centuries in order to show the maximum amount of beauty from each stone - its colour, clarity, brilliance and shape.
Before the 16th century diamonds were usually left in their natural octahedral shape and when set looked rather lifeless. The major source of diamonds in the old world was India, and with the opening of trade between western europe and the Orient in the 16th and 17th centuries the flow of diamonds and other gemstones from the east increased rapidly and new forms of cutting were devised. At this time, diamonds were flat cut or table cut and coloured stones might be flat cut or en cabaochon. However this increase in the use of diamonds in western jewellery brought about the rose cut and later the brilliant cut, the brilliant cut being most important and widely used today.
The first brilliant cuts were introduce in the middle of the 17th century. Known as Mazarin's they had 17 facets on the upper half. Vincent Peruzzi, a venetian polisher, later increased the number of facets from 17 to 33. This significantly increased the brilliance of the cut gem, which were already incomparably better than the rose. Generally known as the cushion/old mine cut this form of cutting would never reach its full potential because the bruting process hadn't been developed yet, therefore all stones were rounded squares or rectangles in cross-section rather than circular. This form of cutting was very common by the early 18th century. Sometime later the old european cut was developed, which had a shallower pavilion, different arrangement of facets and more rounded shape. The old european cut was the forerunner of the modern brilliant cut and was the most advanced in the 19th century. Around 1900's an improvement in equipment led to the development of the round brilliant cut. Created in 1919 Marcel Tolkowsky calcuated the Ideal Cut in which up to 50% of the stone can be lost in cutting and polishing however this isn't a perfect technique, and is continually being slightly modified.
Old Diamond Cuts & when they were invented
(A) Point cut/octahedral 1300's (B) Table cut mid 1300's
(C) Old single cut/Old eight cut late 1300's
(D) Briolette cut late 1600's (E) Rose cut 1700's
(F) Old mine cut/Cushion Cut 1800's
(G) European Old Cut 1900's
A) The point cut is one of the very first symetrically faceted cuts. Dictated by the natural shape of octahedral rough diamond.
B) The table cut was a slight modification developed in the mid 1300's in which the majority of the top half is cut away and a table is formed.
C) The old single cut/eight cut invented in the late 1300's has additional corner facets creating an octagonal girdle.
D) In the late 1400's Lodewyk van Berqeum introduced absolute symmetry. He cut lustrous stones in pear shapes with triangular facets on both sides.
E) The rose cut was introduced in Antwerp mid 1500's. It also consists of multiple triangular facets in patterns, but is essentially a crown without a pavilion.
F) The old mine cut/cushion cut is the earliest form of the brilliant cut diamond. Its distinctive characteristic is that it has cushoined/rounded girdle and brilliant style facets.
G) The forerunner for the modern brilliant cut the european old cut was invented in the 1800's and was the most adavnced cut for the decade. This cut has a smaller table, shallower pavilion and more rounded shape.
Modern diamond cutting process
Marking: A rough stone is marked to determind the direction of the grain, eliminate waste and bypass inclusions or imperfections.
Cleaving: Refers to splitting a stone along its grain by striking it. A rough stone is cleaved if there are any inclusions/defect that would prevent it from being made into a single gemstone
Sawing: Cutting the stone into the approxiamte shape required without faceting
Girdling/Bruting: The rough is place in a chuck on a lathe. While the rough stone rotates on the lathe a second diamond on a dop is pressed against it, rounding the rough diamond into a conical shape.
Polishing/Faceting: The polishing and cutting of each facet is accomplished by attaching the stone to a dop stick and pressing it against a revolving lap
Briallianteering: The final cuts made to the stone by a brillianteer