Gem Profile- Glass, Crystal and Quartz

by Judy Ellis

Let's talk Glass, Quartz and Crystal:

A couple of years ago, Dale Armstrong did a series of gem profiles about quartz. In her profiles she touched on several different types of glass that have been labeled as quartz. Technically they were since both quartz and glass have the same base of silicon dioxide (SiO2), however, the main difference between glass, quartz and crystal is the arrangement of the atoms and the basic molecular structure of the material.

Glass is considered an amorphous solid; it doesn't have a crystalline structure and is made primarily of silicon, potash, lime and soda.

Quartz crystals are pure silicon dioxide and found within the earth.

Crystal is made with silicon, sodium and lead, making the atoms in the glass line up and form crystals which allow it to be carved and faceted easier than glass.

In jewelry making, we use all three materials; glass, quartz and crystals. Today I thought it would be nice to touch on all three.

What is Glass?

Glass beads are made from a thin reed, or cane, that is cut, drilled and polished. The most familiar type of glass in jewelry making would probably be the seed bead and fire-polished Czech beads. Czech glass beads are faceted and then put in a furnace to "polish" the rough edges with heat. They have to be careful during the process or the beads will melt. These types of beads are amorphous and are not as bright and don't have the refraction properties of crystal.

What is Quartz?

Quartz, the beautiful and natural stone, comes in a variety of colors from rose to smoky and has been valued throughout the centuries for jewelry and other gemstones. Some of the most familiar quartz gems are Amethyst, Citrine, Smoky and Rose quartz. The color of the quartz depends on the end ions when the Silicon Dioxide was forming into crystals. For example; the iron that creates the beautiful purple in amethyst.

Rose Quartz Necklace. Created by Peggy L. Marzano.

What is Crystal?

Crystal is similar to quartz in that it has a crystalline structure and is also made of silicon dioxide. The only difference is that it is man-made just like a Cubic Zirconium, and is the same chemical composition as diamonds. Crystal is glass made with silicon, sodium and lead. The lead makes the atoms in the glass align turning it from an amorphous solid into a crystal. Anciently, trace amounts of lead were used to color glass, but not enough of a concentration was used to turn the glass to crystal. This process wouldn't be developed until 1676 when an Englishman by the name of George Ravenscroft added lead oxide in a higher concentration making the glass more clear, more durable and able to be carved and faceted into glasses and beads.

This unusual specimen comes from Tibet. Notice not only the exotic crystal scepter growth, but also the clay inclusions within the bottom crystal.

About Crystal:

In 1891 Daniel Swarovski invented a machine to cut and facet crystal beads exploiting the refractive and reflective nature of the crystal to give us Swarovski Crystal. Swarovski Crystal contains up to 32% lead dioxide. The addition of lead to glass not only turns it into a crystal, but also lowers the melting point and makes it softer and easier to carve and facet. It's the lead that gives the crystal the clarity and sparkle we love.

Swarovski crystals

Gem Profile- Glass, Crystal and Quartz

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