Nick on the Rocks: The secret summit of Washington’s Mount Index

The mountain’s namesake granite was used to build Seattle’s iconic Smith Tower and is coveted by climbers. But its peak is made of a much older rock.

Adam Brown

Adam Brown Jun 12, 2025

Dec 27, 2024

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                <h1>Nick on the Rocks: The secret summit of Washington’s Mount Index</h1>
                <h2><p>The mountain’s namesake granite was used to build Seattle’s iconic Smith Tower and is coveted by climbers. But its peak is made of a much older rock.</p></h2>
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               <p>By <a href="/author/adam/">Adam Brown</a></p> 
              <p><time datetime="2025-02-04T05:00:00-08:00">Dec 27, 2024</time></p>
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            <p>There is Index granite all over the Skykomish Valley. From the walls of the Index quarry – known by rock climbers all over the world for its grippy quality – to the towering peak of Mount Index, signs of the granite are everywhere you look in the valley.</p><p>However, the top third of Mount Index itself isn’t granite at all, but a much older and more mysterious igneous rock that formed more than 140 million years ago at the bottom of the ocean.</p><p>Nick Zentner travels all over the valley taking a closer look at the famous granite.</p><p><em>Support for Nick on the Rocks is provided by Pacific Science Center.</em></p>
          </article>

There is Index granite all over the Skykomish Valley. From the walls of the Index quarry – known by rock climbers all over the world for its grippy quality – to the towering peak of Mount Index, signs of the granite are everywhere you look in the valley.

However, the top third of Mount Index itself isn’t granite at all, but a much older and more mysterious igneous rock that formed more than 140 million years ago at the bottom of the ocean.

Nick Zentner travels all over the valley taking a closer look at the famous granite.

Support for Nick on the Rocks is provided by Pacific Science Center.

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By Adam Brown

Adam Spiro Brown manages Original Productions at Cascade PBS. He previously ran Lucid Visual Media, an independent production company, creating award-winning documentaries, films and commercials.