The invention relates to a gemstone according to the independent claim 1. Diamonds are cut in order to create a plurality of re ^¬ flecting facets. A brilliant is a diamond or another gemstone which is cut in a particular form with a plurality of facets. The purpose of the cut is to create a brilliance. Typically, a brilliant has a crown with 33 facets and a lower part, the pa ^¬ vilion, having 25 facets. The girdle between the crown and the pavilion may additionally have facets which are not counted. Traditional brilliants therefore generally have 57 or 58 (if a culet is present) facets.

A major problem in the cutting of diamonds is a dramatic loss of weight as compared to the raw diamond. Typically, weight loss rarely is less than 50%. Less material might theoretically be removed. However, this results in the loss of brilliance.

It is also known to provide cuts with more than 57 facets. E.g. in US D514,978 there is disclosed a gemstone having a pavilion with a heart shape and including 40 facets. This design does not address, however, the problem involved with loss of weight or loss in brilliance.

WO 2009/094432 discloses a rectangular gemstone having a crown with 25 and a pavilion with 40 facets. However, due to the very specific regular arrangement of the facets of the pavilion this design is limited to rectangular stones.

It is therefore the object of the present invention to overcome the drawbacks of the prior art and in particular to provide a gemstone which reduces loss of weight, enhances the brilliance and which can be used for forming gemstones having a round girdle .

According to the invention these objects are solved with a gem- stone according to claim 1.

The gemstone according to the invention comprises a substan ^¬ tially round girdle, a crown extending in a first direction from the girdle and a pavilion extending in a second direction from the girdle. The second direction is opposite from the first di ^¬ rection. The pavilion has 40 facets. It has been found by the inventors that by providing 40 facets on a round girdle gem- stone, the loss of material or weight may be reduced while keep ^¬ ing a high desired brilliance. While this cut is preferred for diamonds it can also be used for other gems.

Preferably the gemstone has a crown with facets which are cut in a brilliant cut, particularly having 33 facets. It has been found by the inventors that the 40 facets pavilion according to the invention is particularly advantageous in context with known brilliant cuts on the crown.

Even more preferably, the girdle is oval, i.e. not exactly cir ^¬ cular. It has been found by the inventors that the pavilion cut having exactly 40 facets is particularly suitable for oval shapes .

Preferably the facets of the pavilion are arranged symmetrically with respect to two planes running through the axis of the gem ^¬ stone and perpendicular to each other. These symmetric planes typically are the planes running through the transverse and the conjugate axis of an oval. Hereinafter these planes are referred to as the transverse and the conjugate plane. These planes form four equal quadrants of the pavilion. It is hereby understood that in view of the mirror symmetry the term "equal quadrants" refers to the number, size and shape of the various facets which are, however, mirrored with respect to these planes in the vari ^¬ ous quadrants. Two diametrically opposing quadrants further are rotationally symmetric with respect to the axis of the gemstone by 180° rotation. Such a regular design is particularly suitable for providing round or oval girdle gemstones.

According to a further preferred embodiment each quadrant com ^¬ prises one centre facet which has four corners. In particularly, preferably each quadrant has exactly one centre facet having four corners .

According to a further preferred embodiment of the invention, each of these centre facets has one side in common with a centre facet of two neighbouring quadrants, respectively. Furthermore, preferably, the centre facets of all quadrants have one common centre corner.

According to a further preferred embodiment each quadrant com ^¬ prises five peripheral facets each having three corners and each extending to the girdle.

Furthermore, the pavilion may comprise two conjugate and two transverse peripheral facets. These facets each have four cor ^¬ ners and are arranged symmetrically to the conjugate or the transverse plane, respectively, so that a centre line of these facets lies within the respective planes. Each of the conjugate and transverse peripheral facets therefore lies within two neighbouring quadrants. Furthermore, these transverse and conju ^¬ gate peripheral facets have one corner arranged at the girdle. This corner typically is in the conjugate or the transverse plane, respectively.

Furthermore, three intermediate triangular facets may be ar ^¬ ranged between the centre facet and the peripheral facets of each quadrant. Preferably, two of the intermediate facets have a joint edge with an intermediate facet of two neighbouring quad ^¬ rants, respectively. Furthermore, in each quadrant two of the intermediate triangular facets have a joint edge with the centre facet of the same quadrant.

The girdle furthermore may be provided with facets, preferably 16 or 32 facets. It is, however, also possible to have a girdle without facets.

According to a further preferred embodiment of the invention, the pavilion has substantially two angles. The first upper angle is relatively large in the range of between 50° and 70°. Even more preferably, this angle is around 60°, most preferably 57°. The pavilion has a second lower angle which is in the range of 20° to 40°, preferably around 30°, most preferably 32°.

The invention will be explained in more detail with respect to the following detailed description and the accompanying drawings in which

Fig. 1 is a side view of a gemstone according to the present in ^¬ vention

Fig. 2 is a bottom view of the gemstone shown in Fig. 1 and Fig. 3 is a top view of the gemstone of Fig. 1. Fig. 1 shows a gemstone 1. The gemstone 1 has an upper crown 20, a girdle 10 and a lower pavilion 30. The gemstone 1 is rotation- ally symmetric around an axis A. The pavilion 30 has two pavil ^¬ ion angles. In an upper area the pavilion angle a is 57°. In a lower area the pavilion angle β is about 32°. The crown 20 and the pavilion 30 have a plurality of facets as will be explained hereinafter with reference to Fig. 2 and Fig. 3. In the embodi ^¬ ment of Fig. 1 the girdle 10 has a plurality of facets 11.

Fig. 2 shows a bottom view of the gemstone 1, i.e. a view of the pavilion 30. The pavilion 30 comprises 40 facets which will be explained hereinafter in detail. The pavilion 30 is mirror symmetric with respect to a first transverse symmetric plane T and second conjugate symmetric plane C. These planes are running through the axis A and are perpendicular to each other. They separate the pavilion 30 into four quadrants Ql, Q2, Q3 and Q4 each having the same arrangements of facets. Hereinafter the ar ^¬ ranged facets will be explained with reference to the first quadrant Ql . The facets in the other quadrants Q2, Q3 and Q4 are arranged in the same manner.

Each quadrant has an inner centre facet 31. The centre facet 31 has four corners. A centre corner 32 is common to the centre facets 31 of all quadrants. The centre corner 32 is lying on the axis A (see Fig. 1) of the gemstone 1. Each of the centre facets 31 has two common edges 33 with centre facets of the neighbour ^¬ ing quadrants. For example the centre facet 31 of the quadrant Ql has one common edge 33 with a centre facet of quadrant Q2 and one common edge 33 with the centre facet of the centre quadrant Q4.

Each quadrant furthermore has five triangular facets 34a, 34b, 34c, 34d, 34e which are arranged at the periphery, i.e. which are reaching to the girdle 10. Four of these triangular peripheral facets 34 (facets 34a, 34b, 34d, 34e) have an edge running along the girdle. A central peripheral facet 34c has one corner arranged at the girdle but no edge along the girdle.

The pavilion 30 furthermore has peripheral facets 35, 36 which are arranged in two neighbouring quadrants. In particular two conjugate peripheral facets 35 are lying in the quadrants Ql, Q4 and the quadrant Q2, Q3 respectively. Two transverse peripheral facets 36 are lying in the quadrants Ql, Q2 and in the quadrants Q4, Q3 respectively. The conjugate and transverse peripheral facets have a centre line which is arranged within the trans ^¬ verse and conjugate planes, respectively.

Three intermediate triangular facets 37a, 37b, 37c are arranged between the centre facet 31 and the peripheral facet 34a, 34b, 34c, 34d, 34e, 35 and 36. Triangular facets 37a, 37c have a joint edge 38 with the corresponding triangular intermediate facets of neighbouring quadrants. These intermediate triangular facets 37a, 37c further have a common edge 39 with the conjugate peripheral facet and the transverse peripheral facet 36, respec ^¬ tively. Furthermore, two of the intermediate triangular facets, namely the facet 37a and 37b have a common edge 40 with the cen ^¬ tre facet 31. Furthermore two intermediate triangular facets, namely the facet 37b and the facet 37c are contacting each other and have a common edge 41.

Fig. 3 shows the crown 20 of the gemstone 1 from the top. The crown has facets cut in a known brilliant cut. 32 facets of tri ^¬ angular or quadrangular shape are arranged around a tablet 21 having eight corners.