Saturday, August 24, 2013

What is "Zentrumite"? Vaseline Glass?

I saw a piece of jewelry today with a stone described as "Zentrumite".  It glows neon green under a black light, and is a pretty, pale green color in other lighting.   It looks sort of like Prehnite in the pictures I saw.


It's VERY pretty!   Zentrumite sounds like a mineral, sort of like dolomite or Prehnite. 

But what is it, really?

Vaseline Glass Beads--natural light
Well, after some research (thanks, google!) I've discovered that it's glass---Vaseline glass to be specific.  All Vaseline glass glows green.  A quick google search reveals that this trademarked Zentrumite is Vaseline glass that is made at the Zentrum Glass Company in Ohio.  They make glowing glass "jewels" for windows, stained glass, things like that.  They have a variety of glass options---blues, greens, reds and ambers.


Vaseline Glass--Black Light

What is Vaseline Glass?
Vaseline glass is yellow or greenish-yellow glass that contains uranium dioxide* as a colorant.  It's also called Uranium Glass.  The uranium content makes the glass fluoresce (glow) bright green under ultraviolet light.  Vaseline glass is a broad category that includes other glass categories:  it encompasses both pressed and blown glass manufactured from 1835 onward and includes  carnival, opalescent, stretch, satin, cased and cut glass.

Vaseline glass was first produced in 1835 in Bohemia, and first made in America in the 1840's by the Boston & Sandwich Glass Company.  It's heyday was the late 1880's through 1905.  After the start of World War II, the United States government curtailed the liberal use of uranium by glass companies.  In 1959, the government's ban was lifted, and since then several glass companies have produced contemporary Vaseline glass.

Vaseline Glass Collectors, Inc. (vaselineglass.org) defines it as follows: (1) it must be yellow or greenish-yellow by daylight; (2) it must fluoresce bright green under a black light; and (3) the glass must contain uranium dioxide (at least 2%).  

I googled "Vaseline glass faceted jewelry" and to my surprise, there is a LOT of this jewelry around, vintage and contemporary, on places like RubyLane and ebay. And on etsy too!  It's VERY pretty, looks like peridot sometimes, and makes some VERY beautiful and interesting jewelry pieces!  I like it a lot.

*My only thought though is....is uranium in glass SAFE?  Uranium Dioxide is radioactive---you can detect Vaseline glass (and Urania-glazed pottery) with a Geiger counter!  I searched around the net for awhile and it seems like the answer is.... it's sort of safe.  It's been tested, and although no one should polish or otherwise cause "dust" from this glass (don't breathe that in!), it's deemed "safe" for touching or wearing, I suppose.  HERE is a website that discusses the testing process, and the readings from a Geiger Counter on assorted glassware and jewelry.  BIG Geiger counter readings on some beads there. This scares me a bit.  I don't know, anything with Uranium.... may not be something I want touching my skin. 

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