The Story of Linde Stars

The following article is based on excerpts from an interview with Mr. Jack Burdick, co-inventor at U.C.C., Linde division.

MJ: Mr. Burdick, would you tell us how you happened to develop the star? 

Burdick: I must go back to about 1920.  In Europe as in all other places since, synthetic blue sapphire has never been a satisfactory material.  Regardless of how you grow it, the color seems to segregate on the outside of the boule.  So in Europe at one time they were attempting to get better distribution of the color in blue sapphire.  They kept adding magnesium oxide to the sapphire until finally they made spinel.  When they made blue spinel, they thought it was blue sapphire.  In fact, it was sold for blue sapphire for a considerable period of time before it was detected that it wasn't blue sapphire at all.  It was spinel.

In about 1947 we were attempting to do the same thing the Europeans were trying to do back in 1925 .  .  . that was, to try to improve the blue sapphire by getting a more uniformly colored material.  You'll remember we said the color of blue sapphire was due to iron and titania.  We thought that perhaps we could eliminate the iron and get the blue color with titania if we properly heat treated the material after we grew it.   So, we left the iron out of the formula and we put only titania in it.  Then our plan was to heat this in a furnace with a reducing atmosphere.  We felt that if we reduced the TiO2 we would be able to get a blue color without the presence of iron.  So we manufactured these sapphires with only titania in them.  We heated them for several days in a furnace at a high temperature.  And when we took them out, they were star sapphires.

However, we didn't recognize them immediately as being such.  But we did see that they were different.  They were slightly milky.  They had some indication that there were different rays within the sapphire.  We didn't know if we had cat's-eyes, if we had stars, or exactly what we had.  However, my brother was an amateur lapidary and had a little shop in his house only a few blocks away.  So I took some of these boules that had been heat treated and grown only with titania as the colorant to his house and told him to cut cabochons from them.  I suggested that if he notice anything particularly, that he should telephone me.

So, this Sunday in late December, 1947, he called me and said he thought these stones looked different.  I went over to his house and looked at them under his fluorescent light.  They did look a little different, but not particularly so.  In the course of the conversation, we decided to go out on the back porch for a cigarette. It was a nice, sunshiny day, even though it was winter.  We carried one of these stones on a dop stick with us.  As we stepped on the porch and the sun hit the dop stick .  .  . there was the star!

So you might say  .  .  . like the Europeans in making spinel  .  .  . they were trying to do something different.  We also, at the time we made stars were trying to do something different.

MJ: Mr. Burdick, Did you have it in mind to create gemstones?

At that time Linde's business was both industrial and jewelry.  However, there were no stars.  Some blue as well as some ruby stones as well as other colors were being sold to lapidaries who made regular faceted gem stones from them.

MJ: Mr. Burdick, Then would you say that the discovery of the star was an accident?

Burdick:  You might say that it was an accident. 

However, some work had been done both by us and by many other people in trying to make stars.  The point is, we were successful when we were trying to do something else.  Had we not been aware of what a star stone was, we might have passed over this thing and never developed it into the business that it is today.  Incidently, we sold about $100,000.00 worth of stars the first six months we made them.  I think this proves that there was a need for them.

MJ:  Can you think of any other facts that you think might interest the jeweler?

Burdick:  It might be interesting to imagine how nature made stars.  We know that in natural stars there is titania present.  We know that in natural stars this titania is present as an independant phase oriented in exactly the same manner as it is in our synthetic stars.  It would be easy to imagine that a natural star was formed at very high temperature in the earth.  And as the earth cooled this crystal went through the temperature range say from 1100 to 1500 degrees Centigrade  .  .  . the difference being that we keep them in that temperature range for a few days. 

But nature kept them in that temperature range for millions of years.  So the thing that causes the asterism in natural and synthetic stars is identical, and you might say that at least some of the processing is identical.

Linde patented their star sapphires in November of 1949.  Production was discontinued in 1974 due to overseas competition.

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