How to Identify Lake Superior Agate

lake superior shoreline rocks with foaming water image by Paul Retherford from Fotolia.com

Lake Superior agate was formed by volcanic eruptions around 1 billion years ago, when continents were dividing. The same movements that created the trough of Lake Superior itself ultimately created the agate, too. Now the state gemstone of Minnesota, Lake Superior agate is often cut and polished as a gemstone. Lake Superior agate needn't be hard to identify; just follow a few simple steps.

Instructions

Difficulty: Moderately Easy

Step 1

Look at the stone's color. Lake Superior agate is typically yellow, brown, red or orange, caused by iron oxidization. If it isn't yellow, brown, red or orange, it almost certainly is not Lake Superior agate.

Step 2

Observe the size of the stone. Most Lake Superior agate is small, from the size of a ball bearing to a golf ball. Lake Superior agate has been known to be as large as a volleyball, but this is highly uncommon. Anything bigger is almost certainly not Lake Superior agate.

Step 3

Look for bands. Most Lake Superior agate is banded. These bands or stripes usually parallel each other, and many form complete circles or other enclosed shapes (called "fortifications"). Some Lake Superior agate features almost perfectly straight bands.

Step 4

Feel the surface. Most raw (unpolished) Lake Superior agate is not smooth-surfaced. If your stone is smooth-surfaced, it likely isn't Lake Superior agate. Smooth specimens of Lake Superior agate are rarely found.

Step 5

Note the geography. Where did you find your stone? Lake Superior agate is, as its name implies, native to the Lake Superior area. If the stone is from somewhere else, it almost assuredly is not Lake Superior agate. The south and west shores of the lake are especially common sources for Lake Superior agate.

Article Written By William Jackson

William Jackson has written, reported and edited professionally for more than 10 years. His work has been published in newspapers, magazines, scholarly journals, high-level government reports, books and online. He holds a master's degree in humanities from Pennsylvania State University.

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