[1] Dichroic glass is a very popular choice with glass artists today, especially so when creating marbles, because of its properties of having more than one color and when viewed from different angles, has a sparkle effect, much like a cut gemstone.
Dichroic glass is actually a product created by the space industry, and was first used as an interference filter for precise scientific measuring.
To create this effect, glass artists use a thin layer of metallic oxides including magnesium, silicon and titanium at high temperatures.
The opposite side is turned into a lens and the entire piece is shaped into a sphere.
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