Thursday, July 22, 2010

Geo-Shopping!: Striped Agate

Welcome to the first in what will hopefully be an on-going series (on-going as long as I have money, I suppose!): Geo-Shopping!

I prefer working with gemstone beads, in all honesty. I'm cool with glass, and I'll deal with plastic/synthetic/ceramic beads grudgingly. Gemstones were my first love and what I really get excited about. Plus, there's plenty of science behind them, too!

I have a lot to work through in my bead box, but I thought I'd start the series off with my latest purchase:

striped agate

Striped Agate

Agates of all kinds form when silica (silicon dioxide) deposits build up in hollow spaces, called vesicules, left behind in rocks. This usually occurs in volcanic rocks, as gases form bubbles and then sneak out, but sometimes vesicules occur in metamorphic rocks as well.

You can have all kinds of agates, depending on temperature, pressure, and what other mineral impurities were mixed in with the silica. Agates come in a variety of bright, clear colors and with different striping patterns. Striped or banded agate like this guy up here happens when there's the "magic balance" between the silica solution and the impurities it contains, resulting in alternating bands of color. Other times you get formations known as "eyes," where a small piece of silica hardens prematurely within the vesicule, around which other silica deposits later form.

eye agate

Agate can also be a replacement mineral in the fossilization process, leaving you with the aptly-named Fossil Agate:

But back to my beads! Their beautiful red/orange color comes from iron oxide impurities that mixed in with the silica solution that formed the original piece of agate oh so long ago. Today, we see iron oxide all the time: it's rust.

Just goes to show that in the right setting, even something as ugly and unattractive as rust can be beautiful and eye-catching. :)

You can read more about agates at Agate Lady.

And browse lots of neat pictures at the following Flickr photostreams (if you want a new desktop background or some inspiration!):



  1. Oooh! Thanks for the gemstone bead porn pictures! They are gorgeous. I like both stone and crystals myself.

  2. hehe, "bead porn"! I work in a bead shop and this is what I see all day. Yum....