📜 Key facts
| Age | About 1.1 billion years old (Midcontinent Rift lava flows) |
|---|---|
| Origin & sources | Lake Superior region of Minnesota, Wisconsin and Michigan. Glaciers spread it through gravels as far south as Iowa. It has been Minnesota's state gemstone since 1969. |
| Composition | Chalcedony banded red, orange and yellow by iron oxides |
How it forms
Gas bubbles in lava from the ancient Midcontinent Rift filled slowly with silica, layer by layer. Ice-age glaciers later ground the basalt away and scattered the hard agates across the upper Midwest.
Mineral data: see Agate.
🌍 Where it's found
- Type locality
- Notable source / deposit
- Country of origin
Marker positions are approximate (region or locality level). Type localities from Wikidata; notable sources curated by Crystopedia.
Learn more
Mineral variety
Orange
RootSacral
Healing crystal
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