Bedrock Mortars for Grinding Acorns


Bedrock mortars are man-made, circular, depressions in a slab of bedrock or isolated boulders that were made by early Native Americans. These depressions, or "holes", were constructed using hand-held, elongate pounding stones called pestles to grind up acorns and other foodstufs into an edible paste or flour. Mortar holes come in a tremendous variety of shapes and sizes, but most are no more than 8 inches deep, with diameters of 4 to 5 inches that took decades, if not hundreds of years, of frequent pounding and grinding to create. Although bedrock mortars were used by stone-age peoples all over the world to prepare food, extensive use of them by North American Indians is limited to California, the Great Basin, and the Southwest. Bedrock mortars are especially associated with California Indians who used them mainly to grind acorns.

Acorns were one of the primary foods of the Suisun, Tolenas and Malaca Indians who lived in the area of Bella Vista Ranch, and there are many bedrock mortar sites where they prepared their acorns by grinding them into an edible paste. There are at least three sites on public land in the Lynch Canyon Open Space Park (Solano Land Trust), but pretty much all of the rest are on private property that is closed to the public. Failure to respect private property can result in a fine and/or jail, and in the old days you risked being shot by a vigilant land owner! So if you want to safely visit a bedrock mortar site, you are more than welcome to take a hike on one the Lynch Canyon trails that lead to bedrock mortar sites. There is also a nice site in the newly established Rockville Trails Preserve that the Solano Land Trust may open to public access in the near future, but for now you need to arrange to go on a guided hike with a Land Trust docent if you want to explore that area. There are also displays of local Indian artifacts at the Pena Adobe Museum.

Below is a link that leads to information on a few of the archaeological sites that you can visit to view some bedrock mortars used by the Suisun and other Indians to grind acorns. There is also a link that leads to where you can learn more about how the Suisun Indians prepared their food, such as the acorns that were such an important part of their diet. Acorns in their natural state taste so incredibly bitter that it makes you wonder why anyone would ever consider eating them in the first place! Lastly we provide a few links to where you can learn more about the artifacts these people made, the clothing they wore, and the dwellings they lived in.










Archaeological Sites of the Patwin People
(including Bedrock Mortar Sites)



Archaeological sites with lots of bedrock mortars are also known as milling stations, and these were where long ago the local native peoples processed acorns - one of their main foods. Below are some bedrock mortar sites and other types of archaeological sites that we know about, organized by the native village that was closest to the site. The best place to see bedrock mortars in the Suisun Valley area is at Lynch Canyon County Park, which was probably the site of an ancient village that is not mentioned in any historical accounts. Here there are 70 or so bedrock mortars concentrated in a small area that is easy to hike to and open to the public. Bedrock mortars in the neighboring Suisun Valley, and to a certain extent in the adjacent foothills, were probably associated with a village near modern Rockville that early Spanish settlers called the village of the Suisun. Hence, the native people here were the Suisune Indians. Sites in the Lagoon Valley area (Pena Adobe), to the east of the Suisune, likely belonged to the "so-called" Malaca Indians, and sites in the foothills between the villages of Suisun and Malaca likely belonged to a people whom the Spaniards named the Tolenas Indians, after their village of Tolen. Information on other bedrock mortar sites in the nearby San Francisco Bay Area can be found on the Bay Area Native Sites website.


Lynch Canyon Sites (Unnamed Patwin Village)
Lynch Canyon Open Space - Tower Trail site (open to the public)
This site is a large flat bedrock slab with 51 mortars and 5 cupules (man-made depressions). The mortar holes are in two concentrations. This is one of the easiest sites to get to in the Suisun Valley area, and it is probably the best.
38.189417, -122.200583
Lynch Canyon Open Space - North Ridge Trail site (open to the public)
This site is located at a large monolithic boulder with a flat vertical face. Four much smaller boulders at the base of the monolith contain 13 bedrock mortars.
38.19391667, -122.2011333
Lynch Canyon Open Space - Upper Middle Valley Trail site (open to the public)
This site is located at a conspicuous outcrop that looks like the prow of a sinking ship. It is also very close to a pioneer homestead site that is in the process of being restored. Four much smaller boulders and a small slab beneath the prow contain 10 bedrock mortars and some cupules. One of the mortar holes (at left) is unusually large.
Suisun Valley Sites (Villages of Suisun and Sonetro)
Martin House (Stonedene Mansion) site (private property - no public access allowed)
This site is a large stone slab, and a nearby isolated outcrop with a total 92 bedrock mortars, mostly in the fenced-in backyard of the Stonedene mansion. The property is presently owned by a development company, but some sort of agreement exists with a non-profit group called the Stonedene Foundation, which was formed to preserve the mansion for future generations. There is presently no public access, but there were plans at one time to make Stonedene an educational facility and museum, so it may open up with limited access in the future.
38.236000, -122.127400
(The photograph on the left from the Bay Area Native Sites website shows the slab several years ago when it had been freshly cleared of dirt and grass to show the mortar holes.)
Rockville Bluffs Petroglyphs (private property - no public access allowed)
A petroglyph panel located somewhere in the Rockville area. Some attribute this panel to Suisun Indians, but it is more likely the work two Algonquin Indians who were part of an expedition led by John C. Fremont that in 1843 passed through the area. The petroglyphs are severely worn from people making paper and chalk rubbings on the soft volcanic rock.
38.248477, -122.132553
(photographs by Rodney Rulofson)
Rockville Hills Regional Park (open to the public)
There are a couple of trail guides that claim there are bedrock mortars here. However, all you are likely to find are gas pockets that formed in volcanic rocks (lower right photo) when the rocks were first born and in a semi-molten state. There is a rain water basin (left photo) with a rusty red stain that some might claim was made by Native Americans grinding up manzanita berries, but we don't buy it. We think the red is just a natural iron-oxide coating and not man-made.
38.245330, -122.140869 (left photo)
38.249883, -122.138322 (right photo)
Rockville Trails Preserve - Green Valley Creek site (docent guided hikes only)
This site is a large slab that has 34 bedrock mortars. It is on land is owned by the Solano Land Trust, which also owns the Lynch Canyon preserve. They plan to open up Rockville Trails to recreational use in the near future when permitting has been obtained and facilities built.
38.275167, -122.150183
Wolfskill Hills Ridge site (private property - no public access allowed)
This site is a small slab with 7 bedrock mortars and 2 cupules. Nearby and across a gully are two large boulders containing 4 more unusually large mortar holes that are probably much older than the others.
38.299092, -122.112536
Tolenas and Lagoon Valley Sites (Villages of Tolen and Malaca)
Tolenas Springs Road site (private property - no public access allowed)
This site has at least 41 bedrock mortars and several cupules in large boulders in the steam bed of Soda Springs Creek. Despite the locale name of Tolenas Springs, it seems more likely that this site was associated with the nearby Patwin village of Malaca, which is only two miles away. Although we don't know for sure the location of Tolen, as urban development has removed all trace of it, the village was probably a few miles to the south, where the city of Fairfield is today.
Pena Adobe site (open to the public)
The Pena Adobe Museum features Indian artifacts inside the building, and outside the museum there are two large boulders with bedrock mortars in them. The boulder shown on the left is at interpretive marker number 8, but it was moved from its original location, which was about 450 feet to the northeast, on the other side of the grass play field. The other boulder (right) sits in front of the adobe.
Hume Grove site (open to the public)
This site is a rock slab with 10 bedrock mortars located near the south side of Hume Grove, which is about 500 yards northeast of the Pena Adobe Museum and just off the paved bike path that starts near the museum. There is also a grooved rock towards the north end of the groove. Several of the rocks here have groove marks made by drill bits and heavy machinery, but this one is special as it was probably created by Native Americans who used it to sharpen sticks and/or stone tools.
38.338830, -122.010266 (right photo - Hume Grove site)








Artifacts of the Suisune People
(Tools & Baskets)


Artifacts (Tools & Baskets)
Shown on the right are three stone mortar bowls that were found either on, or immediately adjacent to Bella Vista Ranch. From left to right: Bella Vista Ranch, Okell Ranch and Andrino Ranch.

(photographs by Mike Clark)

Shown on the right are Patwin Indian baskets in the collection of the Department of Anthroplogy at the University of Calilfornia at Davis (UCD).

(photographs by UCD)

The Patwin baskets above include 1) an open-weave burden basket, 2) a coiled winnowing basket, and 3) & 4) two styles of coiled bowl baskets. Patwin baskets typically had three-rod foundations of peeled willow shoots, with horizontal coils (warps) of willow woven in a left-hand direction, and vertical weaves (wefts) of sedge root (light color), redbud (red), or charcoal-dyed bulrush (black) to make the designs.
Shown on the immediate right are Suisun Indian artifacts that were found in middens (Indian refuse piles) located on or in the area of Bella Vista Ranch. There are also Indian burial grounds, but these are sacred and not to violated. Shown on the far right are Suisun Indian artifacts collected by historian Rodney Rulofson.
Shown above are 1) arrowheads (flat base), 2) birdpoints, 3) spear points (notched base) and two pieces of 4) knives (note the concave profile on the bottom piece). All of these are made of black obsidian, probably from the Santa Rosa area. The white beads, also called 5) wampum, are made from clam shells, and a wide variety are found near Bella Vista Ranch. There are also two dark-gray beads made of soapstone (steatite), and some of the more uniform white beads are made of magnesite. The 6) red white-heart beads, also called Hudson Bay trade beads, are glass beads that are not made by Indians, but were made in the eastern U.S. and brought in by white traders. There are also some 7) other types of glass trade beads. The 8) clam shell pendant was not found in Suisun Valley, but is from the Santa Rosa area, and the 9) eagle claw and 10) elk tooth are modern.
House pits were dug using pointed sticks and digging stones. The sticks were sharpened by drawing them across grooved rocks, like the one at the Hume Grove site. Digging stones were perfectly shaped to hold in ones hand and dig a hole. They were generally more durable than the native sandstone and volcanic rock found in Suisun Valley, which means they probably came from somewhere else.








Food of the Suisune People




Although the Suisune Indians fished the local creeks and the nearby sloughs and marshes all year long, and hunted deer, rabbit, racoons and other game in the grasslands and oak forests, most of their food came from plants, particularly acorns, nuts, seeds, roots, and berries. Women gathered these staples in the Summer and Fall, and because food was plentiful there was no need to farm. If one type of food became scarce with the passing of the seasons, the Suisune simply found another.

Acorn Preparation

Acorns were an important food for almost all California Indians. Women were the main acorn gatherers, and each Fall they hiked to oak groves in the surrounding foothills, hoping to gather the acorns before oak moths infested the trees. They would knock the acorns off the branches using sticks, and pick them up off the ground. Then each woman put a net on her head that was woven like a cap and hung down her back. From this, she suspended a large conical basket, sometimes called a "burden basket", to be filled with acorns for the hike back to camp.

After collecting, the acorns were placed in the sun to dry, then stored in baskets or acorn granaries, sometimes for months at a time. Later, women and children cracked the acorns open with stones to remove the hard shells and smashed the soft "insides" into meal using stone bowls and elongate pounding stones. Often this chore was done on bedrock slabs and boulders, usually near oak trees, using holes in the rocks that are usually referred to as "bedrock mortars". These holes became deeper and deeper with successive poundings over the years, and eventually needed to be replaced by new mortar holes as the old ones became too deep to use. Needless to say, acorn meal often contained grit, which tended to wear down ones teeth.

A bitter acid in the acorns, called tannin, would make one sick, and had to removed before the acorn meal could be eaten. To do this, a hill of sand was made with the center of the hill scooped out and lined with leaves, often from native grapevines. The acorn meal was set on top of the leaves and boiling water poured over this meal several times to leach out the tannin. Another method was to bury the shelled, but otherwise whole acorns, in marshy ground for several months to let the damp soil slowly leach out the acid.

To cook acorn meal, women mixed it with water in tightly woven baskets to make a mush and heated the mush with hot stones from the fire. These stones were dropped into baskets using sticks that were bent and tied together with sinew or twine from plant fibers to form loops. Constant stirring was required lest the hot stones burn through the bottom of the baskets. The acorn meal could also be made into dough and cooked on hot rocks, or rolled into hard balls to carry on a journey.

Piñon Nuts

Pine nuts were another important food that was eaten raw or ground into meal. Because the Pinyon (Piñon) Pines from which these nuts were collected grew in the higher foothills, well above the oak trees, the Suisun probably needed permission from neighboring tribes to collect this staple. However, ancient agreements existed between tribes, and permission for the harvest was seldom denied.

Harvesting was done in the Fall, when the small cones were full of pitch and ready to open. Men knocked the cones down from the trees using sticks with willow branches lashed into V-shaped forks on the ends. Women and children gathered the cones in large cone-shaped baskets, suspended these "burdon baskets" on their backs with head nets, and hauled them to temporary camps near the pine groves.

Back at camp, the cones were piled high in a fire pit, and roasted on hot coals with frequent turning until the cones popped open, allowing the nuts inside to be shaken free. However, soft brown shells encasing the inner fruit of the nuts still needed to be removed. To do this, the nuts were mixed with some hot coals on flat round baskets called winnowing trays, and both coals and nuts tossed repeatedly into the air with swirling motions. When the shells became hard, crisp and dark brown, the coals were removed, the nuts placed in a stone mortar hole, and pounded with a stone pestle to crack the shells.

Some of the cracked nuts - now translucent, soft, yellow-orange and quite delicious - were eaten raw. The rest were returned to the basket trays to winnow out the husks, with repeated tossings and swirlings until the wind carried off the remaining shells. Coals were then added back and roasting repeated until the nuts became dry, hard, and somewhat darker than before.

The nuts could now be stored in large above-ground storage baskets for later use, provided squirels and other vermin didn't get to the baskets first. Some of the dried nuts were eaten raw, but most were ground into flour using an elongate rolling stone called a "mano" on a flat grinding stone known as a "metate". When enough flour was available, it was added to water and the mixture warmed by dropping hot stones into it to make a thick, pine-nut mush that was bit bland on its own, but became quite a feast when berries, roots, leaves, and possibly some chopped meat or fish were added.

Other Foods

Tule Grass from the sloughs, and grasses, sage and other bushes from the fields and brush provided seeds that could be ground or eaten raw. Grass seeds were collected in the Fall using flat baskets, called seed beaters, which scooped the tops of grasses to strip off the seeds. A type of sage brush called chia produced an oily, but very tasty seed, that was collected in the summer. Mesquite bushes produced long, pod-like beans that were also collected in summer, when the pods were still green. The pods were dried, stored like acorns in baskets, then ground in stone mortar bowls for mush, baking dough, or mixed with water to make a drink. Other seeds were usually ground into flour using the stone "manos" and "metates" we described above.

There were also tubers and roots from tule grass, cattails, and dandelions that were edible, as well as berries from manzanita, junipers, and the red Toyon (Christmas) berries. All could be eaten raw or ground up and seeped in boiling water for tea.

Fish and game provided variety, but were supplements, not staples, of the Suisune diet. Almost anything that moved was fair game, but not the coyote or grizzly bear, as they were sacred. Small fresh-water clams that proliferate in the sloughs and creek banks were collected, and crayfish caught in baited traps. Grasshoppers that later plagued white settlers were harvested by the Suisune in the late summer, and when toasted provided a tasty treat. Indeed, the Suisun Valley provided many delicacies, and even though life for the Suisune was hard, and their lives short, food was seldom scarce.







Clothing of the Suisune People


Patwin clothing was minimal, to say the least. Stephen Powers (1877) writes in "Tribes of California" that when he was among the Patwin, "on the plains all adult males, and children up to ten or twelve, went perfectly naked, while the women wore only a narrow slip of deer-skin around the waist. In the mountains where it was somewhat cooler, the women made for themselves short petticoats from the inner bark of the Cottonwood." Shown on the right is a drawing made from personal observation by Henry B. Brown in 1851 or 1852 of Patwin women wearing skirts of deerskin. The middle woman has a burden basket on her back, and a winnowing basket in her hand. (from the Huntington Library Collection)

Although men generally went naked, they might wear fur capes with antler horn caps to camouflage themselves on the hunt, and perhaps an elk hide skirt along with a body armor made of several upright sticks held together by twine to protect themselves in battle. They also wore their hair long, coiled on top of their head, and secured with a hair pin of bone. The drawings below show clothing styles of various California Indian men that are probably illustrative of the types of clothing that the Indians of Suisun Valley wore (when they did wear something).

Yukut (Yokut) men near the San Francisco Mission
by Louis Choris (1816)

Ohlone Man in deer hunting regalia
by Dan Liddell (1992)

Pomo Warrior dressed for battle
by Edward Curtis? (c.1920s)








Shelter of the Suisune People




Most Patwin villages were groups of dome-shaped huts, with dwelling huts that families lived in being anywhere from 15 to 20 feet in diameter. There would also be a few ceremonial and/or meeting lodges that were somewhat larger. Temporary huts that were used for food gathering-camps had inner frames of four to seven poles, and outer walls made of just woven grass mats and/or sheets of bark, whereas the permanent huts of the villages were similar, but with a covering of mud and dirt several inches thick on top of the roof and walls. Stephen Powers (1877) writes in his Patwin chapter in "Tribes of California" that he observed that Patwin hut builders "excavated about two feet [into the ground], banked up the earth enough to keep out the water, and threw the remainder on the roof dome-shaped. In a lodge thus covered a mere handful of sprigs would heat the air agreeably all day. In the mountains where wood was more abundant they frequently put on no roofing of earth."

The illustration above and left by Powers (1877, Fig. 21) is titled "earth lodges of the Sacramento Valley". Notice that it shows entry into the permanent dwelling huts from a central hole in the roofs of the structures. The drawing below of a Patwin village on the Sacramento River by Henry Brown in 1852 shows the same type of entry into the huts by going through a hole in the roof. By contrast, the illustration above and right by William Huff shows temporary dwelling huts with entry made from openings on the sides. Note the door of woven grass mats laying against the outside wall of the hut in the foreground. A dirt-covered ceremonial lodge is in the center of the huts.