Mortar Rock Park Bouldering

A small yet dense collection of quality routes, approximately 100 ft. up the hill from Indian rock. This is a bouldering area, and some of the routes may be considered highball.

The area is usually in the shade, with help from some large trees that hide most of the rock from Indian Rock Ave.

Descent is a simple walk off the back using the steps.

If you're up to it, Nat's Taverse (V8) is a must do.

Nat's Traverse, along with Grizzly Peak Traverse at Grizzly Peak Boulders and Gomers Pile at Cragmont Park, make up what was called the Triple Crown. The real challenge was to do all three in one session, and run between them (though driving is probably acceptable these days). For extra credit do all three three times each.

Park History

See this Berkeley Side article about the significance of Mortar Rock and Indian Rock to the native Ohlone people. Do not damage any mortars you may come across.

Mortar Rock Park was a gift to the City of Berkeley from Mason-McDuffie Real Estate Company during its development of the Northbrae area. The company owner, Duncan McDuffie was a real estate mogul, but among other things, he was a mountaineer and served as the Sierra Club president. It was dedicated for park purposes in 1917.

Geology

Mortar Rock is comprised of a type of Rhyolite that is unique to the hills of Berkeley. Named Northbrae Rhyolite by Andrew Lawson in 1914, after the residential neighborhood in which these rock formations can be seen.

Rhyolite is a type of igneous rock, which means it is solidified magma or lava. It is classified as being felsic (rich in feldspar and quartz minerals), and porphyritic (larger/coarse mineral composition that is visible to the naked eye). The size of the mineral composition is based on how slow the magma cools, which is relative to how deep within the earth it is. The deeper the magma pocket, the slower it cools allowing the minerals time to become larger. The Northbrae variety is far more porphyritic than most rhyolite. 

Mortar Rock also contains many large feldspar mineral deposits on its top edge, which are commonplace in many igneous rocks but no less aesthetically pleasing . They can be seen and admired (and frequently grabbed) while assisting you in toping out your proj. Yes some of these are also quartz (the glassy looking ones), but most are orthoclase or plagioclase feldspar (white, opaque and blocky). Next time you send, say thank you Feldspar.

Park and Climbing Etiquette

Remember this is also a public park in the middle of a neighborhood. Make sure to pick up after yourself (if need be pick up after others), and be friendly and courteous to any non-climbers. Don't forget to cheer others on and make this a fun and inviting climbing area for everyone, regardless of climbing ability.