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Flame fusion Sapphire


#1

Does anyone know exactly what a ‘flame fusion sapphire’ is? Pat


#2

Hi Pat,

Flame fusion sapphire (or any corundum for that matter) is the
original synthetic. It’s made by passing aluminum oxide powder with
the necessary trace elements for the desired color through a high
temp flame. As the powder goes through the flame, it’s melted. When
it exits the flame, it falls on a rotating stage below the flame &
powder source. As it cools, it forms a boule (round rod) that grows
in length as more molten alox falls on it. As the rod grows in
length, the rotating stage lowers to keep the distance between the
flame & the boule uniform.

The flame fusion method of making corundum is sometimes called the
Verneuil (sp?) method after the man that invented it in the late
1800’s in France.

Dave


#3

Pat, you’ll probably get 100 replies to this question. Flame fusion
is one process for making SYNTHETIC mineral crystals. aka Czochralski
process. See encyclopedia article at:

David Barzilay
Lord of the Rings
607 S Hill St Ste 850
Los Angeles, CA 90014-1718
213-488-9157


#4

Hi,

Flame fusion is the earliest process of making synthetic gemstone in
large amounts; developed in the late 19th early 20th century by
Auguste Verneuil of France. Aluminium oxide powder with appropriate
colorants to yield ruby or sapphire is dropped through an (I believe)
oxy-hydrogen flame, fuses, and collects in a boule which is gradually
lowered as the ruby or sapphire grows on its top. It is somewhat like
growing a candle using droplets of molten wax.

Cheers,
Hans Durstling
Moncton, Canada


#5
  Flame fusion is one process for making SYNTHETIC mineral
crystals. aka Czochralski process. 

Not quite, David.

Flame fusion usually refers to the Verneuil process of sapphire or
spinel manufacture, whereby powdered raw material is sifted down
through an oxy-hydrogen flame, which melts it, the flame ending
above or playing on the end of a ceramic rod, on which the molten
material accumulates and solidifies, forming a solid mass. As the
mass grows, the rod is rotated and lowered, forming a carrot or
finger shaped piece of synthetic material. It’s characterized, for
identification, by typical curved growth lines and gas bubbles, and
is, or at least used to me, by far the most common and inexpensive
form of synthetic sapphire and ruby, being widely used in such
things as the typical stones in class rings, inexpensive birthstone
jewelry, and industrial uses such as bearings (the jeweled bearings
in a watch generally are flame fusion ruby). The process was first
devised by the French chemist, Auguste Verneuil, who first described
it in a private paper to the Paris Academy of Sciences in 1891, and
publicly published it in 1902.

The Czochralski process is generally called a “pulling” method, not
flame fusion, since it involves touching a seed crystal to the
surface of a pool of molten material and slowly withdrawing the seed,
which drags a crystal from the melt when it’s done just right. The
crucible of molten material is generally kept that way via induction
melting, not a torch. It was discovered (as links from your article
describe) in 1917, but was for a long time used only to produce metal
crystals. Today, it’s single largest use, so far as I can find, is
in the production of the silicon crystals used in semiconductors.
Production of synthetic gem materials like ruby using the method
didn’t start until sometime after world war 2, though I can’t find
just when. The method is used to produce very high quality, very pure
material (much better than that produced by flame fusion methods),
such as required for laser rods. It is also used for synthetic gems,
and may have surpassed flame fusion methods, at least for ruby, though
I don’t know this, just guessing. It tends to be more costly,
however, to produce material this way, though it’s also capable of
producing larger sizes. Czochralski ruby (I’m not familiar with
sapphires produced this way, though I’m sure it can be) is different
from typical flame fusion material in that, for one thing, growth
lines are not curved. In fact, growth lines generally are impossible
to find at all. The samples of the stuff i’ve studied generally had
virtually no inclusions or identifiable features internally, even at
rather high magnification. But I’ve only studied a few of them, so
others may vary.

cheers

Peter


#6

A stone produced by the Verneuil process see:

http://ist-socrates.berkeley.edu/~eps2/wisc/gemsynthesis.html


#7
Does anyone know exactly what a 'flame fusion sapphire' is? 

One of the cheapest synthetic materials you can mention in gemology.
the various cheap synthetic sapphire or synthetic spinel stones used
in things like cheap birthstone jewelry, or in class rings, are made
by sifting (for sapphire or ruby) powdered alumina, plus whatever is
needed for coloring, down through an oxy-hydrogen flame, onto a
ceramic rod. The rod is rotating and lowering slowly, so the powder
falling through the flame melts, lands on the end of the rod where
an existing puddle of the stuff is already there, and as the rod
rotates and lowers away from the flame, it solidifies into a single
carrot shaped piece called a Boule. about the size of a large
finger, usually. That is either flame fusion ruby or flame fusion
sapphire (or spinel, if that’s the chemistry of the powder used.)

The process is one of the oldest gem synthesis methods around,
Dating from the late 1800s, and certainly the cheapest, with the
finished stones selling for at most a few dollars, usually. The
rough material often sells for around ten cents a carat or less. (or
at least it used to. haven’t bought any for quite a while…)

hope that helps.

peter


#8

Flame fusion is the process of dropping alumina powder down a tube
into a oxy-hydrogen flame where the oxygen is greater than needed to
totally burn the hydrogen. The melted alumina oxide forms a boule
which is slowly lowered out of the flame where it forms corundum.
This is the earliest form of widely manufactured synthetic corundum.
With a dopants of various types added you get a range of colors.
Interestingly, synthetic spinel, which is a kissing cousin to
corundum was soon developed using the flame fusion method.

Richard, in stormy Michigan, where the thunder storms are marching.


#9

Peter, Of course you’re right. I was confusing the two processes.
mea culpa.

David Barzilay
Lord of the Rings
607 S Hill St Ste 850
Los Angeles, CA 90014-1718
213-488-9157


#10

Thank you all for replying to my post about ‘Flame fusion sapphire’.
All your replies were most instructive and educational. I find it
quite fascinating that such gems are listed at and demand a high
price on Ebay, when they are obviously in the actual very low price
range.

Regards to all Orchidians
Pat