Note: Descriptions are shown in the official language in which they were submitted.
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MODIFIED PRINCESS CUT DIAMOND HAVING HEARTS AND
ARROWS PATTERN AND METHOD
FIELD OF THE INVENTION
The present invention is an improvement to the modified princess cut diamond
described in US Patent No. 7,992,410 for forming a princess cut diamond
possessing
a hearts and arrows pattern characteristic substantially equivalent to the
hearts and
arrows pattern in an ideal round cut diamond.
BACKGROUND OF THE INVENTION
The beauty of a properly cut diamond gemstone derives from the manner in
which the cut facets of the diamond reflect and refract light. Diamonds may be
cut
into many different geometrical patterns which are known in the art as the
round cut,
oval cut, pear cut, marquis cut, princess cut, emerald cut, etc. The most
popular
diamond cut is the standard round cut because of its brilliance and optical
light
handling properties. Although caret weight and clarity are factors which will
affect the
value of the diamond independent of cut geometry, the most significant value
is
attributed to its optical properties and color.
A gemologist will refer to the optical properties of a diamond cut using terms
of
art such as brilliance, scintillation and symmetry. Brilliance and
scintillation
correspond to the intensity of returned light, and scintillation and symmetry
relate to
the cut parameters of the diamond and the degree to which the cut facets are
aligned. To provide the highest possible level of scintillation with minimal
loss in
brilliance when analyzed with a brilliance scope, a diamond must possess cut
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parameters which are as close to perfect as possible. A brilliance scope is
currently
used by most grading institutes, such as the Gemological Institute of America
(GIA)
and the American Gemological Society (AGS), for analyzing the loss of
brilliance on
an ideal cut round diamond. Both of these institutes, among others, specialize
in
grading the most valuable diamonds and the best cut grades available.
The most valuable round cut diamond with the best cut grade possesses what
is known to those skilled in the art as a "true hearts and arrows pattern'. A
round cut
diamond will invariably display a "hearts and arrows pattern", but only when
the
pattern is symmetrically cut will it display a "true hearts and arrows
pattern" as known
to those skilled in the art. Heretofore, a "true hearts and arrows pattern"
could be
achieved only in the round cut diamond. The symmetry requirement necessary for
the hearts and arrows pattern to be "true" requires the cut diamond, once
polished, to
possess exacting requirements upon examination by an experienced gemologist
using a 100X microscope so that the facets will be perfectly aligned and meet
each
other at a point. Until the present invention a diamond could not be cut into
the
princess pattern and provide the true hearts and arrows characteristic of the
ideal
round diamond.
SUMMARY OF THE INVENTION
Accordingly, there is provided a modified princess cut diamond having a
symmetrical shape possessing a hearts and arrows pattern characteristic of the
true
hearts and arrows pattern in a round cut diamond comprising: a tablet facet, 4
main
crown facets, 8 crown halves, 8 crown star facets, 4 subsidiary crown facets,
8
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subsidiary crown halves, 8 main pavilion facets, 4 subsidiary pavilion facets,
16
pavilion facet halves and a girdle with each main crown facet having a pair of
crown
star facets symmetrically disposed on one side thereof adjacent to the table
facet,
and a pair of main crown halves symmetrically disposed on the opposite side
thereof,
with each pair of crown star facets having a side thereof adjoining the table
facet
meeting at a point equal to essentially half the longer distance of the main
crown
facet measured horizontally, and with all crown star facets having identical
polished
angles and with the subsidiary crown halves adjacent each main crown facet
having
identical polished angles measured from the surface of the table facet to a
maximum
tolerance of 0.3 , with each of the crown halves polished into alignment with
each
other and into alignment with the pavilion facet halves, and that the
subsidiary crown
halves are aligned in common at each end of the diamond to form a cut corner
in the
diamond at each such end thereof, with each of the subsidiary crown halves at
each
end of the diamond, having a polished angle smaller than the main crown halves
for
forming an included angle of 45 with an abutting one of the adjacent main
crown
halves, and wherein the angle of the pavilion halves is steeper than the main
pavilion
angle.
The modified princess cut diamond in accordance with the present invention
does not include the subsidiary cut-corner pavilion facets a2 of US Patent No.
7,992,410. As indicated in US Patent No. 7,992,410, subsidiary cut-corner
pavilion
facets are not required to obtain the hearts and arrows pattern nor is it
essential for
the girdle thickness across the diamond to be the same.
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The present invention is also directed to a method for polishing a diamond to
form a modified princess cut diamond which will display a hearts and arrows
pattern
comprising: a tablet facet, 4 main crown facets, 8 crown halves, 8 crown star
facets,
4 subsidiary crown facets, 8 subsidiary crown halves, 8 main pavilion facets,
4
subsidiary pavilion facets, 16 pavilion facet halves, and a girdle with each
main crown
facet having a pair of crown star facets symmetrically disposed on one side
thereof
adjacent to the table facet, and a pair of main crown halves symmetrically
disposed
on the opposite side thereof, wherein the princess cut possesses a hearts and
arrows
pattern characteristic of the true hearts and arrows pattern in a round cut
diamond,
said method comprising the steps of: polishing the subsidiary crown facets to
be
smaller in length than the length of the crown halves, polishing the
subsidiary crown
halves to lie at a 450 angle relative to the adjacent crown half, polishing
each of the
crown halves into alignment with each other and into alignment with the
pavilion half
facets, and with the crown halves forming an included angle a which is larger
than
the adjacent included angle 13 formed by the subsidiary crown facets on the
cut
corner sides of the diamond, so as to allow the crown halves to be of equal
size and
the subsidiary crown halves to be of equal size, and wherein the angle of the
pavilion
halves is steeper than the main pavilion angle, the crown halves are at an
angle
steeper than the angle of the main crown angles and the total depth of the
princess
cut is between 68%-71% wherein total depth in %=height/width x 100, wherein
height
is measured from the table fact to a culet and width a diameter of the girdle.
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The main crown and main pavilion facets having the following cut angles:
main pavilion angles 40.60 -41
main crown angles 34.00-350;
subsidiary pavilion angles 64 -67 ; and
subsidiary crown angles 33.5 -34.5 .
To develop perfect symmetry it is preferred that the following additional
parameters be satisfied: (1) the angles of the pavilion halves are 1.2 larger
than the
main pavilion angles; (2) the angles of the crown halves should be 3.8 larger
than
the main crown angles and (3) the crown star angles should be 4 -5 flatter
than the
main crown angles.
It is also significant to the method of the present invention that all facets
be cut
with a small angle tolerance such that the angle difference between all
pavilion
angles are smaller than 0.30 and the angle tolerance between the four main
crown
facets are smaller than 0.40 and the angle tolerance between the four
subsidiary
crown facets are smaller than 0.30.
BRIEF DESCRIPTION OF THE DRAWINGS
Other advantages will become apparent from the following detailed
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description of the invention when read in conjunction with the accompanying
drawings of which:
Fig. 1A is a front view of the princess cut diamond of the present
invention;
Fig. 13 is a top view of the princess cut diamond of Figure 1A;
Fig. 1C is a bottom view of the princess cut diamond of Figure IA;
Fig. 2A is a top view of the princess cut of the present invention at an early
first preliminary stage of development in accordance with the present
invention;
Fig. 2B is another top view of the princess cut similar to Figure IA at a
final
development stage in accordance with the present invention;
Fig. 2C is another bottom view of the princess cut similar to Figure 1A at a
final development stage in accordance with the present invention;
Fig. 3A and Fig. 3B show a true hearts and arrows pattern in an ideal round
cut diamond;
Figs. 3C and 3D show examples of unacceptable hearts and arrows patterns
adjacent to perfect hearts and arrows patterns;
Figs. 4A and 4B shows the hearts and arrow pattern, respectively, for the
princess cut diamond according to the present invention
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Fig 5A is a front view of an alternate embodiment of the princess cut diamond
of the present invention;
Fig 56 is a top view of the princess cut diamond of Figure 5A; and
Fig. 5C is a bottom view of the princess cut diamond of Figure 5A.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
A diamond is a crystal which functions as a prism for dispersing light by
means of reflection and refraction. When properly cut, a diamond possesses
brilliancy characteristics highly attractive to the human eye. The princess
cut
diamond 10 of the present invention is shown in Figures 1A, 16 and 1C
respectively
and includes a crown portion 12 representing the top of the diamond, a
pavilion
portion 14 located below the crown portion and a girdle (g) which separates
the
crown portion 12 from the pavilion portion 14.Figures 5A,5B and 5C is
alternate
embodiment of the invention using the same reference numbers where the facets
are identical. In fact the only distinction between the embodiment of Figures
1A, 113
and 1C and the alternate embodiment of Figures 5A, 5B and 5C, respectively, is
the
omission of the three small subsidiary pavilion facets (a2) on the cut corner
pavilion
sides shown in Figures 1A and 1C respectively. These three facets do not
contribute
to the creation of the hearts and arrows pattern.
The crown portion 12 includes a flat table facet (TF) which is the uppermost
and largest surface of the cut diamond, four main crown facets, symmetrically
arranged around the flat table facet (TF) and four subsidiary crown facets (d)
which
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are symmetrically arranged at each corner of the diamond 10 between the main
crown facets (c) and represent the four corner facets of the diamond. Each of
the
four main crown facets (c) are cut on the side of the flat table facet (TF) to
form two
crown stars (c3) and on the opposite side thereof to form two crown halves
(ci). Each
subsidiary crown facet (d) of the princess cut of the present invention
includes two
subsidiary crown halves (c2) with the subsidiary crown halves (02) being
aligned in
common at one end to form the cut corner sides of the diamond. Each of the
subsidiary crown halves (02) on the cut corner side form an included angle of
450
with an abutting one of the crown halves (c). The parameters and polishing
requirements to form a princess cut in accordance with the present invention
will be
discussed in greater detail hereafter.
The two crown stars (c3) formed from each main crown facet (c) on the side
abutting the table facet (TF) are in alignment meeting at a point essentially
equal to
half the distance of the adjoining main crown facet (c) measured
longitudinally. The
two crown halves (C1) form a square edge on the side of the main crown
opposite
the table facet (TF). The eight (8) main crown halves (c1), the eight (8)
subsidiary
crown halves (c2) and the eight (8) facet crown stars (03) all have the shape
of a
triangle. The outer perimeter of the diamond 10 thus has eight sides inclusive
of the
four main crown sides formed by the eight (8) main facet crown halves (c1 )
and the
four cut corner sides (d) formed by the eight (8) subsidiary crown halves (C2)
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The girdle (g) which separates the crown portion 12 and the pavilion portion
14 has four main girdle facets which lie in a plane perpendicular to the plane
of the
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flat table facet (TF) and may have four subsidiary cut corner facets. The
height of the
crown portion 12 is measured vertically from the flat table facet (TF) to the
girdle (g).
The pavilion portion 14 extends from the girdle (g) to a point 16, known as
the culet,
representing a distance commonly referred to as the pavilion depth. The
pavilion
portion 14 of the diamond 10 is illustrated in the bottom view Figure 1C and
in figure
5C for the alternate embodiment and consists of eight main pavilion facets (a)
which
terminate at the culet 16, sixteen (16) pavilion facet halves (al) and four
(4)
subsidiary pavilion facets (b). In the embodiment of Figure 1C eight (8)
subsidiary
pavilion cut corner side facets (a2) exist and four (4) facets (cc) referred
to as girdle
facets which, as is more clearly shown in Figures 1 A and IC, lie adjacent to
the
girdle (g). In the alternate embodiment as shown in Figures 5A, B and C the
eight (8)
subsidiary pavilion cut corner side facets (a2) and the four facets (cc) are
omitted.
It is apparent from Figures 2A-2C that the eight sides of the princess cut
diamond 10 are not of equal length. As is shown in Figure 2A the square side A
is
longer than the cut corner side B with the main angles a polished so that a>
13 with
the cut corner main angle flatter than the main angle on the square side by
0.8 -
1.2 , This difference in size between the main facets (c) on the square sides
and on
the cut corner sides enables the development of the hearts and arrows pattern
in a
princess cut as will be further explained hereafter.
In Figure 1B, the crown star facets (c3) are shown present only on the square
sides of the diamond with each of the crown halves (ci) on the square sides
being
longer than the subsidiary crown halves (c2) on the cut corner sides. The main
crown
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facets (c) and the corner crown facets (d) are polished to give the princess
cut of the
present invention a square appearance with the main crown and pavilion facets
cut
at very precise angles.
To a gemologist, cut is the most important factor affecting the beauty of a
diamond. The round shaped diamond can be cut into a near perfect round shape
with symmetrical facets causing a hearts and arrows pattern to appear. The
hearts
and arrows pattern can be readily viewed from the pavilion end of the diamond
when
light is illuminated on the table facet side. A true hearts and arrows pattern
is
considered the ultimate in cutting precision and is illustrated for the round
cut in
figures 3A and 3B. As is evident from figures 3A and 3B, an eight-fold-
symmetry
about an axis passing through the center of the table and the culet 16 exists
with
eight hearts and eight arrows with figure 3A showing 8 symmetrical hearts and
figure
3B showing 8 symmetrical arrows. The "hearts" are clearly visible along the
axis of
symmetry of the diamond from the pavilion end with light illuminated at the
table end
and the "arrows pattern" is visible from the diamond at the table end when
light is
illuminated at the pavilion end. Figures 3C and 3D show examples of
unacceptable
hearts and arrows patterns adjacent a perfect hearts and arrows pattern.
The hearts and arrows pattern will result on a cut round diamond only when
the following requirements are met:
o The shape of the diamond is symmetrical.
o 8 main crown and 24 subsidiary crown facets.
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- 8 main bottom and 16 subsidiary bottom facets.
o All main facets (crown 8: bottom) have to be polished at a perfect 45
angle
to each other.
o All facets are perfectly aligned.
o All the bottom main facets are of equal size and at an angle ranging from
40.6%41.0%
o All the bottom subsidiary facets are of equal size and at an angle which
exactly 1.20 steeper than the main facets (main bottom angle 40.6 -41.0
subsidiary 41 8 -42.2 ).
- All the main crown facets are of equal size and at an angle ranging from
33.8 -35.1 and are perfectly aligned on the main bottom facets.
Al! the subsidiary crown facets are of equal size and perfectly aligned on the
main crown and subsidiary bottom facets and polished at an equal angle.
o The cut proportions should be as follows:
total depth 59.4%-62.4%
crown height 14.5%-1 6.0%
girdle thickness 1.5%-2.95%
Roundness 99.0%-1 00%
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Table size: 53.0%-57.5%
Total depth in % = height /width)( 100
where height is measured from the table facet (TF) to the culet and
where width is the diameter of the girdle
Angle discrepancy between main facets are smaller than 1 and less than
0.5 between subsidiary facets
It is extremely difficult to generate a hearts and arrows pattern in a
princess
cut due to the fact that the square shape of the princess cut is less
symmetrical than
the round cut, the number of facets are different and light reflects
differently.
Moreover, for a princess cut it is necessary to have a minimum of eight main
crowns,
represented by the combination of main and subsidiary crown facets and that
each
main crown should have a parallel main opposite crown. The difficulties in
forming a
true hearts and arrows pattern for a princess cut have been resolved in
accordance
with the present invention by polishing the cut corner sides (d) smaller than
the four
main sides as explained above in connection with figure 28 so that an
octagonal
geometry having equal sides is prevented when viewing the diamond 10 from the
table side and to allow the polishing of all of the subsidiary crown halves
facets (c2)
on each of the cut corner sides at an angle of exactly 45 degree; i.e., the
included
angle existing between the subsidiary crown halves facets (c2) on the cut
corner
sides and the crown halve main facets (ci) on the square sides should be
exactly
450. In addition the eight star facets (c3) which abut the table are polished
while
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leaving the four subsidiary crown facets (d) on the cut corner sides
untouched. In
addition, as explained above in connection with Figure 2C the subsidiary
pavilion
facets on the cut corner side are polished at a steeper (greater) angle than
on the
longer subsidiary pavilion square sides so that > (p.
The following additional parameter requirements should be met to obtain a
true hearts and arrows pattern in the princess cut:
- Total Depth 68%-71 % measured similarly to the round cut with the width
measurement being the girdle dimension longitudinally
a Pavilion Depth 51%-53,5%
o Crown Height 14%-1 5.5%
o Table Size 53%-59%
o Girdle Thickness 1%-3.5%
The Hearts & Arrows pattern will appear without distortion if the cut
parameters fall between the above ranges and the main crown and pavilion
facets
are cut to the following very precise angles:
- Main Pavilion angles 40.6 -41 .0
a Main Crown angles 34.0 -35.2
a Subsidiary Pavilion angles 64 -6T
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Subsidiary crown angles 33.5 -34.5 .
The angles of the Pavilion Halves are 1.2 steeper than the main pavilion
angle.
o Crown Halves have angles that are 3.8 -4.2 steeper than the main crown
angles.
o Crown Star angles are 4 -5 flatter than main crown angles.
Furthermore, it is essential for all the facets be cut to a very small angle
tolerance, i.e. the angle difference between all pavilion angles has to be
smaller than
0.3 and the angle tolerance between the four main crown facets must be
smaller
than 0.4 and 0.3 for the four subsidiary crown facets.
When all of the above is accomplished the manufacturing of the Princess
Hearts & Arrows diamond will have a near perfect symmetry provided that the
polishing meets the following additional requirements:
All polished crown and pavilion facets be of equal size, a tolerance of 0.04%
is allowed between the various facets;
o The Culet (point of the diamond) has to be perfectly centered with a
tolerance of 0,03%;
o The shape of the diamond, as determined from the girdle; i.e., the four
main
girdle facets and the four subsidiary girdle facets (the ones in the corners)
should be
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such that they are polished to be at a 45 degree angle relative to one another
with a
tolerance of 0.030 allowed; and
The four main girdle facets have to be identical in length so that when
measured the result shows a length/width ratio of 1.00; a tolerance of 0.035
is
allowed.
When all of the above mentioned cut parameters are observed the stone is
ready to undergo the final polishing process steps which will give the stone
its
brilliance and allow for the Hearts & arrows pattern to appear:
o Pavilion halves must be polished to near perfect symmetry and depth and
be perfectly aligned with each other;
- Crown Halves must be polished to near perfect symmetry and depth and be
perfectly aligned with each other and perfectly aligned with the Pavilion
Halves; and
o Crown Stars must be polished to near perfect symmetry and must join
each other at exactly half the distance of the main crown facet.
All stars and halves are to be polished with identical angles, a maximum
tolerance of 0.30 is allowed.
When all of the facets of the princess diamond are cut following the above
procedure a hearts and arrows pattern will be achieved having the hearts and
arrows characteristic of an ideal round cut diamond. Moreover, the modified
princess
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cut diamond of the present invention not only possesses a hearts and arrows
pattern'
but exhibits a straight edge square shape. Figures 4A and 4B show the hearts
and
arrow pattern of the modified princess diamond cut according to the present
invention.
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