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Gem cuts


#1

In looking at faceted a couple of questions come to
mind about standardization.

  1. What are the usual cuts and what do they mean? I have seen
    references to belly cuts, german cuts and shallow cuts. When
    choosing stones to fit a setting, how does one decide on the cut?

  2. Are calibrated faceted stones cut to standards? Are all 8 X
    6 ovals very nearly the same size?

Thanks for any answers,

Bob B


#2
In looking at faceted a couple of questions come to
mind about standardization.
1) What are the usual cuts and what do they mean? 

round, oval, pear, marquise, cushion, and emerald. the pear is
like a tear drop, the marquise (also called navette) has two
points like a double ended boat, cushion is like a rectangle, and
emerald is like a rectangle with cut corners. There are many more
cuts, but these are the usuals…

 I have seen
references to belly cuts, german cuts and shallow cuts.  When
choosing stones to fit a setting, how does one decide on the
cut?

depends on the stone, and whether synthetic or genuine. Genuine
stones, especially the more expensive, can vary widely from
standards as they are usually cut to maximize the weight.
Inexpensive genuine stones are frequently cut to calibrated
standards. Genuine stones can be cut very deep or very shallow
and still conform to calibrated standards, and this can affect
the setting you should choose. Synthetic stones are usually quite
close in dimensions. Decide on the cut you like the look of, oval
is the most common cut of colored stones, followed by round > >

  2) Are calibrated faceted stones cut to standards? 
     Are all 8 X 6 ovals very nearly the same size?

Once again, this depends on if the stones are genuine or
synthetic, with the difference mainly in the depth. If a stone is
labeled as an 8x6, it should definitely be 8x6. Genuine stones
will frequently show variance, especially as they increase in
price
Hanuman
The Ganoksin Project


#3

Belly cuts refers to stones cut with a fat underbelly to retain
weight and color,and as fashion in certain parts of the
world.Against the 90 degree girdle of the cut stone the second
row on the pavilion(bottom) of the stone might be cut at 80
degrees,then 75 degrees,65,55 and so on with the final culet
facet at a sharp 10-20 degrees to close the stone.These are also
refered to as “native cuts” in the mistaken opinion that the
cutters had only primative tools or lack of ability.When in
reality they will pick up 40% additional weight recovery and
several shades of color.And also it is the preferred and popular
cut in the country of origin.Often these cuts are made at the
request of westerners in countries like Sri Lanka and India
where the export of unworked,unpolished stones,such as sapphires
is forbidden.The are looked upon as “preforms” to be recut in
western centers.

German cuts used to refer to style very similar,but more well
preportioned They also cut the pavilion very steep for the same
reasons,weight retention and color.But the angles used were more
to the liking of western eyes.From 90 Degree pavilion to say 60
degrees,50 degrees,40 degrees and still a slight “window” with a
closing facet under the critical angle.This referred to German
hand cuts prior to 1970.These days German cuts can be machine
cuts on automatic machinary,or even stones cut to critical angle
with proper preportions in Bangkok or Chinese factories under the
supervision of German managers.In any of these later connotations
of "German"cut it has come to refer to in the trade as the
highest standard of commercial cutting.

In answer to your last question,calibrated stones,in theory,are
supposed to be exactly within .10mm of the size.But in practise
there can be quite a varience.Even the German Edus or Lux
automatic faceting machines,which make the most uniform stones in
the world,there can be a difference of several tenths of a
millimeter from stones attached on one end of the rack to the
other.

                                   Mark Liccini
     LICCINI

Gemstone Rough Dealers since 1970 U.S.MAIL
E-Mail: @Mark_Liccini1 224 7th St.#2B
http://www.LICCINI.com Jersey City,N.J.07302 Voice
Mail/Fax: 201-795-1115