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How to Identify Michigan Agates

Agates are precious gemstones that form when liquid quartz fills a pocket in another rock such as lava. Agates are found all over Michigan, especially along shorelines after a storm, in gravel pits and mines, or along the road in a construction zone. Patterns, colors and banding vary according to temperature and pressure changes while agate forms; because of these changes and differences in mineral content, no two agates are identical. While many agates resemble other gemstones, they have many distinctive qualities that help collectors identify them among other stones.

Things You'll Need

Field guide
Flashlight
Pocket knife

Instructions

- 1
  Visit one of Michigan's museums or rock shops for agate samples, maps or advice that will lead you to a good spot to locate agate. Take a class that helps you identify the characteristics that make agate stand out from other rocks.
- 2
  Buy an illustrated field guide on Michigan rocks or check one out at the library. Good field guides have written descriptions and photos or illustrations of all types of rocks in their natural state. Field guides are handy to carry with you when you look for agates.
- 3
  Pick up a gray rock less than 3 inches in diameter that you think may be agate, and weigh it against a different type of rock. Agate is noticeably heavier than most rocks.
- 4
  Hold a rock up in the sunlight or shine a flashlight on it. If it's agate, you should see a soft, translucent glow from the quartz in the agate. Squat on a shoreline facing the sun and look across the rocks lying just on the waterline. Agate reflects more light than other rocks.
- 5
  Look at chipped or broken rocks for a glossy, waxy look or smooth natural surface. Search for patterns such as straight parallel bands or small round eyes. Look for unbroken rocks that are pitted or have a surface texture like that of a potato.
- 6
  Scrape a rock that you think is agate with the blade of a pocket knife. Agate is a hard rock that won't scratch.

Rocks & Minerals