Day #86 Outcrop: Half Dome Granodiorite Erratic

We’ve visited the Half Dome Granodiorite before, both as a crushed “sand” and as a deskcrop. Well, it’s time to visit this beautiful rock once again, this time in the form of a glacial erratic, in its natural habitat.

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Half Dome Granodiorite Erratic

This particular erratic is located on the shores of Tenaya Lake in Yosemite National Park. It’s an example of the equigranular phase of the Half Dome Granodiorite (there’s also a porphyritic phase). If we take a closer look you can see some of the minerals that make up this rock: plagioclase feldspar is most abundant, followed by quartz, K-feldspar, hornblende and biotite. There’s also accessory sphene (titanite) but I doubt you’ll spot it at this resolution.

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Take a Closer Look at its Minerals

And I’d be remiss if I didn’t let you in on the even more spectacular view from this vantage point.

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Tenaya Lake and Polly Dome

Explore this and all of my 2010 Deskcrops and Outcrops in Google Earth!

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