Everyone's thought is probably the same when they first see Balancing Rock.
How does that large, heavy boulder stay where it is?
Balancing Rock is along the Knobcone Point Road trail in the southeastern corner of Mount Diablo State Park.
The eroded sandstone rock must weigh at least a ton and sits precariously atop a smaller rock of similiar material.
It seems like it would fall over at some point, but if you shove on it, the rock doesn't even budge a millimeter.
It makes you wonder how the 1989 Loma Prieta earthquake didn't shake it loose or why it hasn't fallen during a windy winter rainstorm.
Ken Lavin, a local naturalist and a board member on the Mount Diablo Interpretive Society, had this information:
"The sandstone that forms Balancing Rock was originally granitic rock in the Sierra Nevada. The granodiorite was weathered and eroded during the Eocene Epoch, 50 million years ago. The quartz sand particles were carried by rivers flowing west and dumped into offshore ocean basins where Mount Diablo stands today. The quartz sand is cemeted together by calcium carbonate. Rain water seeping into the rock redistributed the cement and resulted in the uneven weathering that produced balancing rock. So in a way, Balancing Rock is related to Half Dome!"
A replica of Balancing Rock is on display at the Lindsay Museum in Walnut Creek.
The hike to get to Balancing Rock is a bit strenous.
The easiest route is to start at Curry Point on the mountain's southern side. Take the main dirt trail there for a tenth of a mile until you hit the Knobcone Point Road trail. Stay on that trail for 1.75 miles and you will find Balancing Road at the top of one of the many rolling hills on the mountain's lower southern flank.
A warning. The hike has a number of hills and there isn't much shade. Don't attempt it if you aren't in at least decent shape and be sure to bring plenty of water.
Your reward will be this peculiar rock that not a lot of people get to see.