Bazu

Hexagon Carre arrondi (see below)

Bazu_diamond_hex_replica

Bazu_diamond_blue_rounded_square_replica

Specifications

Weight:

32.62 carats

Dimensions:

17.74 x 12.44 deep (hex)
22.88 x 21.56 x 8.95 (CA)

Color:

Colorless (hex)
Light blue (CA)

Weight of Rough:

Unknown

Origin:

India or Brazil

Date Found:

Unknown

Current Location:

Stolen in 1792, not recovered

Details

The Bazu was a diamond of 32.62 carats.  It has only been mentioned once in history, but what a place!  It was the largest diamond set with the French Blue in an ornament called The Order of the Golden Fleece, considered to be the most lavish and expensive single piece of jewelry in all of Europe.  King Louis XV had this piece created around 1749 using the French Blue diamond, the Bazu, five ~5 carat brilliant diamonds, the 107.88 Cote de Bretagne spinel, three ~10 ct yellow sapphires, and several hundred multi-point sized diamonds. 

The Golden Fleece was stolen along with many of the French Crown Jewels in September 1792.  It was apparently broken up, with the French Blue recut into the Hope diamond.  The Cote de Bretagne spinel was recovered many years later.  All other stones disappeared into the historical fog. 

The Bazu diamond is one of those elusive historical stones of which little is known, and what is known is contradictory.  There are two stones referred to as the Bazu, with the one in the Golden Fleece already mentioned.  The second was a colorless stone that started as a 104 carat piece of rough that was described as very rotten, with many flaws and carbon inclusions.  This was fashioned into an 8 carat diamond that has subsequently disappeared.

The Bazu set in the Fleece actually has two recorded versions.  The first has been described by Morel (1988) and Bari (2001) as a hexagonal colorless stone weighing 32.62 metric carats, reported by Bapst (1889) as drawn by Hirtz.  So it seems that the experts agree on the physical description of this diamond.

But is their analysis correct?  The only problem with this scenario is that there was no diamond of hexagonal form listed in the Crown Jewels inventory of 1791 (Bion).  There was, however, a stone described as “Un tres grand diamant brilliant, carre arrondi, d’eau un peu celeste  .  .  . “, or “A very grand brilliant diamond, rounded square, a color of a very light sky blue  .  .  .”, with a weight of 31 12/16 cts, or 32.62 metric carats.  (This is the CA form above, for carre arrondi, or rounded square.) This is the only diamond that could possibly have been in the Fleece, as all historical weights match, and no other diamond even comes close to the accepted weight.

So why the discrepancy, and which shape is correct?  Unfortunately, neither Morel nor Bari mention the logic of their conclusions.  There were two drawings of the Fleece done around 1749 by Jacquemin, the court jeweler.  One version shows the Bazu as hexagonal, the other as carre arrondi.  Interestingly, both versions are colored slightly blue. It is thought that these two drawings might have been design drawings, used to show what the Fleece was to look like rather than documentation created to show the Bazu.

Regardless of which shape is correct, line drawings are notoriously inaccurate regardless of the source.  Tillander (1995) shows six different versions of the Sancy, a stone well-documented for several hundred years.  Compare the line drawings of several diamonds done by Tillander and Bauer (1968), or the seven different versions of the Florentine diamond found in many sources.  They may be a close approximation of reality, but are not necessarily an accurate reflection of reality.  So how to resolve this issue to create a replica of the Bazu?  Since both the hexagonal and carre arrondi forms are mentioned by valid authorities, the tie breaker should be the 1791 inventory.  This was ordered by the King, and he would demand the utmost accuracy for all entries.  In this case, there was a team of people involved, and when entries were made by one, another would verify the accuracy of the information, so entries into the inventory must be considered accurate.  This means that the Bazu is not a colorless hexagon, but a very slightly blue rounded square of 32.62 carats. (This is gone into further detail in Farges et al (2009)).

If this logic is correct, then Jacquemin’s drawing of the carre arrondi form can be used as a template.  But it just shows the facet pattern of the crown, and no information about pavilion depth or its facet pattern.  More analysis of the historical record was required to create the replica above.  Morel stated that the Bazu was cut so shallow that it could not be recut to improve brilliance without a significant loss of weight (lending credence to the rounded square form, as a hexagon must be deep due to geometrical requirements).  Jacquemin’s drawing contained both the French Blue and the Bazu, and knowing the dimensions of the FB, those of the Bazu could be inferred.  Now it is just a matter of using these dimensions and modeling a stone of undefined depth to encapsulate the volume to get the required weight.  As it turns out, a depth of 8.95 mm satisfies both the weight and thinness requirements.  A guess, but at least an educated one.

But what about the facet pattern?  There is no stone in any French inventory mentioning the Bazu by name.  The 1691 inventory (Brisson, 1787) lists a ~42 ct table cut diamond (no color is given, and this is the stone Bari believes was cut into the hexagonal Bazu), otherwise there is no other diamond that could be it.  So the Bazu was probably bought and/or cut in the 1700’s in time to appear in the 1791 inventory.  This limits the number of facet patterns for a “rounded square” stone.  There are many variations, but Jacquemin’s drawing implies an Old Mine cut, and that is what was used here.