Photo by Fred Ward.
Florentine Pair: Left stone is
modeled after
a hatpin photo c. 1900 supposedly of the Florentine and
described by Tillander.
Right stone is modeled after a line
drawing by Tavernier. |
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The Florentine is one of those elusive stones that is difficult to track
down. In Tillander’s book, p. 199, there are six line drawings of
different versions of the stone as described by different sources. Tavernier
has provided one of the earliest references to it in the 1600’s. Cletscher
drew it in the early 1700’s from some unknown source, but it is
a more rounded stone. Bauer around 1900 has his version. All
three of these lived contemporaneously with the stone and may
have viewed it first-hand (certainly Tavernier).Their
facet patterns are similar, yet their outlines are different. |
And then there is the
low-resolution photograph of it in a hatpin taken around 1900, assuming
it is the Florentine, that has yet a different shape and a similar facet
pattern. Which to believe?
I
am assuming that the photo is the real Florentine, as the shape and
facet pattern bear at least some resemblance to the various line
drawings. If the photo was taken around 1900, it is quite possible it
is the Florentine as the stone disappeared at the close of WWI. Both
the photo and all line drawings, plus descriptions given by the various
authors, indicate that it is a Double Dutch Rose cut. This style of
cutting uses triangular shaped facets all around, and the top and bottom
of the stone are similarly faceted. All graphic references indicate
this.
If
the photo is considered genuine, then it’s outline can be used for
modeling. Unfortunately, there is not enough detail in the photo to
discern all the facets, but those that are visible suggest the Double
Dutch Rose style. Bauer’s drawing most closely resemble the photo, but
are his drawings accurate? Fortunately, he published a series of
drawings of 14 other diamonds. Analysis of these stones show that he
has a consistent track record for accuracy. Tavernier seems to be
accurate in his drawing of the Great Table, as reported by Sir Harford Brydges in 1794 when he handled the stone and commented it was exactly
as Tavernier described. However, there is evidence that Tavernier may
have made some mistakes in other stones, so he has not been considered
the authority in this case. The other sources mentioned have not had
their authority as well established as Bauer, so their inputs are
relegated to more of an advisory role.
The replica described here is the result of an effort in 1981 to create
it using Tavernier’s description. Although the line drawing existed in
many sources, they were not considered accurate in stone dimensions due
to scaling effects in printing copies of the original. It was desired
to use a drawing from an original manuscript. Fortunately, one of seven
in the United States existed in a university library about an hour away
from where I was living.
Dimensions and facet pattern were taken from the drawing (below). Since
this was before the personal computer and graphics programs, everything
had to be done manually. Index settings were easy to calculate, angles
were more problematic. Since the stone was described as a double Dutch
rose cut, symmetrical on top and bottom, this made calculations slightly
easier, as now only the top half of the stone had to be resolved.
The weight reported by Tavernier was 137.27 carats. Assuming an average
specific gravity of 3.51 g/cc for diamond, the required volume for half
the stone was 3.91 grams. (This was before the difference between old
and new carats was known.) A side view of the stone equates to a cone
of low angle sitting on top of a truncated cone of a higher angle. All
that was necessary was to find the angles of the two cones.
The resultant effort to get from this equation to determining the angle
of the upper and lower cones took three years. There were many steps
where the solution seemed unattainable, and required considerable
thought. The delay was no problem, as large CZ of the color, purity,
and degree of perfection was extremely difficult to make at the time and
it took that long for the manufacturer to fill the order.
The final equation to solve was 11.06=7tan σ + tany. Unfortunately,
this resulted in a single equation with two unknowns, where the unknown
σ was the angle of the lower cone and y the angle of the upper cone. This was resolved by iterating the values of σ and comparing them with
the resultant value of y. As it turned out, σ could only range from
54-56°, as outside of this y could not be resolved. This information
was used to calculate the other data necessary to cut the replica.
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