The Story of Chlorastrolite, Our State Gemstone

Michigan’s Hidden Treasure

Did you know Michigan is home to a gemstone so unique it can’t be found anywhere else in the world? Meet chlorastrolite, also called Isle Royale greenstone. With its striking starburst patterns and turtle-shell-like appearance, it’s no wonder Chlorastrolite was named the “official state gem” of Michigan with Public Act 56 of 1972. Thanks to the passionate efforts of the lapidary community and a signature from Governor William G. Milliken, chlorastrolite secured its place in Michigan’s history and hearts. Let’s dive into what makes this gemstone so extraordinary and how it came to symbolize our Great Lakes State.

Chlorastrolite: A One-of-a-Kind Gemstone

What is Chlorastrolite?

Chlorastrolite is a variety of the mineral pumpellyite, formed in the cavities of ancient basaltic lava. Its name means “green star stone,” a nod to its translucent, fibrous structure that scatters light into mesmerizing starburst patterns. Some stones even show a distinctive mosaic pattern that resembles a turtle’s shell, making it a favorite among collectors.

A Billion Years in the Making

The origins of chlorastrolite date back 1.1 billion years to the Midcontinent Rift System. This was when a massive geological event that created Michigan’s unique terrain happen. Lava flows from this rift formed the rocks of the Keweenaw Peninsula and Isle Royale, where the gemstone is found today. Over time, erosion and glaciation revealed these ancient rocks, bringing chlorastrolite to light.

Where to Find It

While chlorastrolite is most famously associated with Isle Royale, collecting it there has been prohibited since 2000 to protect the national park’s ecosystem. However, rockhounds can still search for this gemstone in the copper mining spoil piles scattered across the Keweenaw Peninsula. Large pieces are rare, but finding even a small greenstone pebble is a treasure worth the hunt!

A Lapidary Favorite

Thanks to its unique appearance and rarity, chlorastrolite is often cut and polished into beautiful jewelry, from rings to necklaces. Its chatoyant, tiger-eye-like quality makes it especially eye-catching, whether it’s light green from Isle Royale or the darker tones typical of Keweenaw specimens.

Chlorastrolite isn’t just a gemstone; it’s a piece of Michigan’s rich geological and cultural heritage. From its billion-year-old origins to its designation as the state gemstone in 1973, it tells a story of natural wonder and local pride. Whether you’re a seasoned rockhound or a curious visitor to Michigan’s Upper Peninsula, the greenstone serves as a sparkling reminder of the beauty and history beneath our feet. Next time you’re in the Keweenaw Peninsula, keep your eyes peeled—you might just find a little piece of Michigan magic.

Marisa Fancy along with her husband and four children dreamt of moving “Up North”. They had vacationed for years in northern Michigan and in 1995 they finally made the move.

The family was always out exploring, but with 4 kids there was some limitations on what they could do. Marisa discovered the amazing network of trails in Northern Michigan after Steve died and she would walk for miles. The trails provided her with peace, comfort and solitude at a difficult time in her life. Later, after meeting Guy who would become her second husband, she learned to golf and found another passion she could enjoy in beautiful Northern Michigan.

Marisa has been the family historian, writer, and poet for as long as she can remember. She has always loved to write and has now found a creative outlet for it other than family. You can read her articles in Adventures in Northern Michigan, Northern Michigan History and Golf Up North.