This view along forest road 41N03 near Callahan, California shows outcroppings of natural cement beneath the thin rocky peridotite soil.  It is truly an unusual formation as there are other deposits of it within areas of ultramafic peridotite in the region.  The following information below is copied from another nearby site called Cement Banks, to which I took this panorama there: https://www.360cities.net/image/banks  

During the Ice Age, glaciers formed along the tops and down the slopes of the Klamath Mountains. Ice flowed into the valleys, carving the landscape into its current appearance. There are all sorts of glacial features to be found in the forest.

Glaciers are vast sheets of perennial ice that undergo downhill movement. As a glacier moves, it often incorporates rocks of various sizes into its icy matrix. Rocks that travel through the ice are sculpted and rounded over time, later to be deposited as till or moraines. Moraines are unsorted piles of glacial rocks along the side (lateral), in front (terminal) or along the bottom (ground) of the glacier.

There are many ways in which glaciers erode the land. Sometimes they erode the features that they create, which may have taken place at Cement Banks. The rocks seen there were deposited by the glacier, perhaps underneath the ice, classifying it as a ground moraine. Rocks and cobbles in the deposit are partially rounded and unsorted and originated from nearby cirques. Most of these rocks are peridotite, which is a dark green volcanic rock. Others are granodiorite, which are similar to granite. How Cement Banks became eroded after its initial deposition is still in question. One idea is that after deposition, the moraine was eroded by the glacier.

As a glacier flows over a ridge, there is a lot of pressure on the uphill side and the higher pressure melts some of the ice. The lower pressure on the downhill side of the feature causes the water to refreeze. Refreezing causes expansion, further fracturing the rock on the downhill side, eventually loosening cobbles until they are carried off by the glacier. This process is called plucking and can create a feature known as a roche moutonnée.

An alternative explanation for this landform is that it was formed by debris flows from rock debris spilling off the east side of the East Boulder Creek Glacier into Cement Creek.

Either during or after the glacial features were created, the cobbles and boulders were cemented together. What made the matrix hard is silica (SiO2) and possibly calcium carbonate (CaCO3), which was dissolved in the water that trickled through the rocks. This water may have come from the melting glaciers, or perhaps it was groundwater. Either way, the silica or calcium carbonate precipitated onto the rocks and in the mud—like matrix to cement the whole feature together and preserve it as seen today.

Source: https://www.fs.usda.gov/detail/klamath/specialplaces/?cid=stelprdb5116577