Diamond cut is an another important factor that determined value of Diamond. Diamond cut doesn't mean that shape of Diamond ( Round, Oval , etc.) , Diamond cut refers to the proportions of the parts of the diamond and how well the diamond reflects light.  Diamonds cut is the important factor  to maximize the sparkle, fire, brilliance and overall visual beauty of a diamond . 
                        Rough diamonds have little to no sparkle. This is because they lack facets or faces that bounce and reflect light. Diamonds sparkle is a result of light performance.  The angles, locations, sizes and shapes of facets will determine the diamond sparkle.

A diamond’s cut impacts two aspects of the diamond ’s optical and physical properties: 

The Optical properties  of Diamond  means  a Diamond how it interacts with light. it is overall face up appearance. its related with quality of polish of diamond 

a) Luster: Its ability to reflect a high percentage of the light that strikes their surface.  Luster is directly related to the hardness of the stone and the quality of its polish.

b) Brightness:


The amount of white light that is returned to the eye from both internal and external surfaces. Brilliance is determined by the quality of the diamond’s polish and the number and size of inclusions inside the gem. 

c) Fire : The display of spectral ( rainbow ) colors seen coming from the inside of a diamond. the visibility of all these colors is what gives diamonds a unique beauty.

d) Scintillation: A diamond will show scintillation, or “sparkle,” when movement is involved. The viewer, the light source or the diamond itself must be in motion for scintillation to occur.


Physical properties of Diamond mean assess a diamond's design and craftsmanship , its related with  anatomy of Diamond. 

Symmetry of Diamond , Weight ratio , durability  and polish are four important  Physical properties of Diamond

Symmetry of Diamond  : Symmetry refers to how well the facets and angles of the diamond align, Since the sparkle and beauty of a diamond are determined by how well light reflects through it.

Types Of Symmetry Defects : 

 1) Out of Round Diamond  : The round cut diamond is not well shaped and the ratio of length to width of diamond.

 2) Table Off Center : Deviation of the table from the central position on the crown, the light performance of diamond will effected. 

 3) Culet off Center : Deviation of the culet from the central position on the pavilion
Not Parallel Table and Gridline Wavy girdle - Undulating girdle. The girdle isn't in the straight line around the diamond. This can affect the evenness of a diamond's setting.

 Girdle Thickness Variation 


Misalignment - Displacement of the crown and pavilion facets in relation to each other


Non-pointing - Fully formed facet that does not reach its prescribed location (short facet) or is incompletely finished (open facet), resulting in adjoining facets not meeting at precise points.

Misshapen facet - Difference in shape or size between one facet and another of the same type; or distortion of a given facet.


Non-octagonal table - The table is not a regular octagon; results in misshapen star and bezel facets.

Missing facet - Asymmetrically missing or deleted facet.

Natural - Part of the original rough diamond's surface that remains on the polished diamond; typically causes an out-of-round girdle outline, short facets or misshapen facets.

Extra facet - Additional facet placed without regard for symmetry and not part of the standard cutting style; typically causes an out-of-round outline, short facets or misshapen facets.


Diamond Cut Grading : 

Excellent (or Ideal) Cut :
                            This  Diamond is considered as high quality of Diamond. it was most Brilliance , Fire,  Scintillation . Light moving through an ideal cut diamond bounces almost fully back out the top of the stone and brings its brilliance into view . the diamond's facets are perfectly sized and proportioned. The location of the diamond's attributes, such as culet, girdle table, etc. are in all the perfect locations. The diamond is not out of shape. The diamond can achieve an Excellent cut grade.

Very Good (or Fine) Cut : 
                                     Very Good offer slightly less brilliance and scintillation than the excellent cut. Very brilliant with minimal light leakage .The diamond's facet sizes and proportionately are near perfect. There may be one or two disproportionate elements that are viewed under 10px magnification. The impact on the diamond Cut grade and sparkle are minimal. The diamond can still achieve an Excellent cut grade.
                                    
Good Cut :
                                    Diamonds classified as Good, usually allow some light to escape during the reflective process. The size or location of attributes and facets is slightly disproportionate. The sparkle of the diamond is affected, as a result. The diamond can achieve a Very Good cut grade, at best.

Fair (or Shallow) Cut : 
                                        Light moving through a shallow cut diamond is lost out of the bottom of the stone and the lack of light play makes shallow cut diamonds appear lifeless. The poor sparkle performance of diamonds classified as Fair cut may be noticeable to the untrained eye, and are for this reason also less costly. 

Poor (or Deep) Cut : 
                                            Light moving through a deep cut diamond escapes out from the sides, darkening all or most portions of the stone. The poor sparkle performance of diamonds classified as Poor cut may be noticeable to the untrained eye, and are for this reason also less costly. The facets and proportionately are noticeably imperfect. In non-round shapes, the shaping is not perfect. The diamond's sparkle and brilliance are impacted adversely and the diamond can achieve, at best, a Good cut grade. A diamond with poor symmetry may misdirect light that travels into the diamond, sending it off at slightly wrong angles, and thereby reducing the diamond's brilliance.

 


Brilliant Cut Diamond V/s Single Cut Diamond  V/s  Old European cut diamond

Round Brilliant Cut Diamond :
                    Round Brilliant Cut Diamond its also called Fall Cut Diamond , It is a cut in a particular form with numerous facets so as to have exceptional brilliance, The standard cut for round brilliant diamonds contains 57 or 58 facets, strategically placed to enhance the light performance of the stone.  when the brilliant cut had developed into a style with a circular face-up outline, it had passed through many variations in facet size and proportions. These included table size, crown height, length of the lower half facets, total depth, and culet size.


 

Single Cut Diamond  :
                    

                     The Single Cut is a simplistic diamond cut, and is a historic cut like the Old Cut and Rose Cut. Single Cut Diamond its also called melee Diamond , Melee refers to round diamonds that typically weigh less than 0.10ct or 10 points , The Single Cut variety of melee are vintage round diamonds that have 17 facets in total. Single cut melee feature an 8/8 facet arrangement with 8 facets along the crown (top) and 8 facets on the pavilion (bottom) of a diamond plus a table facet for a total of 17 facets.



 Old European cut diamond : 

 An old European cut diamond is a round diamond primarily  , These antique diamonds