Archaeological Sites

Anvil holes are shallow bedrock depressions, also known as cupules, that typically are paired with a much deeper, bedrock mortar hole. These shallow depressions were probably used by Native Americans to help crack open the shells of pine nuts and/or acorns with a hand-held stone to get at the nut meat inside. The meat was then placed in an adjacent bedrock mortar hole to be ground up into an edible paste.
Bathtubs - see Bedrock Basins.
Bedrock Basins are deep depressions 3- or 4-feet in diameter and several inches deep found clustered together in granite bedrock slabs at several locations in the southern Sierra Nevadas. They are also called Indian Bathrubs, and their origin is somewhat controversial, as some believe they are natural weathering features. However, most archaeologists and geologists who have actually studied these features believe they are man-made (Moore et al., 2008). Evidence of a man-made origin include similar size, shape, and elevation range; close association with middens and bedrock mortars; and south- to west-facing locations in a food-rich belt with pleasant summer weather. Experiments indicate that campfires built on granite slabs would have weakened the bedrock beneath to facilitate excavation of the basins using grinding stones. These basins were probably used to prepare food, mainly acorns and pine nuts, with perhaps subsequent storage as well. A group of more than 350 bedrock basins along the Mokelumne River at a site above Salt Springs Reservoir in the Sierra Nevadas apparently were used by Native Americans to make salt by evaporating water from nearby salt springs, which would leave a residue of salt behind in the basins. However, these salt collection basins appear to have different, generally deeper, shapes than the more typical basins elsewhere that are referred to as "Indian Bathtubs".
Bedrock Mortars are man-made holes that were ground and pounded into rock slabs and boulders over many years, perhaps even decades or centuries, using stone pounding tools called pestles. They are much like the stone mortar bowls and pestles of well-stocked modern-day kitchens. Most mortar holes are a few inches across in diameter, and 3 or 4 times deeper than wide. They were generally used to grind up various foods - mainly acorns and different nuts, but also berries, roots and dried meats. Mortars were also used to grind up pigments for making paints to create pictographs, decorate bodies, and mark items such as clothing and tools. Portable bedrock mortars in small rocks that could be carried by hand are called stone mortar bowls, an example of which is shown on the right.
Burial Grounds throughout much of history have been defiled by artifact hunters. Because these places are sacred to the descendants of those whose ashes or remains are interred there, burial grounds should never be entered, nor the locations revealed.
Cupules are shallow depressions in bedrock slabs, rock faces and boulders that are clearly man made, but much too shallow to function as bedrock mortars. Most are an inch or so deep and 4 inches or less in diameter. Many of these are undoubtedly bedrock mortars in the making. Others that are found decorating prayer stones may be decorative or religious in origin. Cupules paired with bedrock mortar holes are probably anvil holes used to help crack open the shells of nuts and acorns to get at the edible nut meat inside.
Dimpled Rocks - see Prayer Stones.
Fire Rings and Fire Platforms are circles of stones that were used either to contain camp fires, or platforms that fires were built on top of. Fire rings may be associated with house pits, or simply placed out in the open. Fire platforms were generally used inside a dwelling hut or ceremonial lodge to elevate a fire off the floor, either to add extra warmth, or to keep children from playing with the embers.
Grooved Stones were used to sharpen sticks for one purpose or another, and are identified by narrow grooves, sometimes parallel, more often times not, within which the sticks were dragged back and forth to put a sharp point on them. Some grooved stones were used to straighten arrow shafts, and some were used to make discs of shell beads a uniform size. Parallel grooves of uniform thickness, of an inch or more diameter, and equally spaced, are more likely created by modern machinery, than hand made by Indians. Machine-made grooved stones include those made by the blades of bulldozers and road graders, as well as holes made by rock drills in large boulders for placing charges of dynamite when building roads and clearing work sites.
House Pits are the subterranean floors of dwelling huts, ceremonial lodges, sweat house and menstrual huts. They are what remains after the structure above collapses, and the wood and grass components of the structures rot away to reveal the sunken floors beneath.
Indian Bathtubs - see Bedrock Basins.
Leaching Stations or Leaching Basins are shallow, smooth-bottomed, bedrock depressions of man-made origin that were used to leach bitter acids out of ground-up acorns, or other foods. They are generally several inches across, and an inch or two deep, and they can be difficult to distinguish from rainwater basins that formed during natural weathering processes. In fact, some may have originally been rainwater basins that were converted without alteration into leaching basins. Others were clearly modified by grinding down the base of the basin using a grinding stone called a mano. Ground-up foods were placed in the basins and water poured through them to leach out any bitter acids, and these acids in some cases have stained the smooth bottoms of the basins to a reddish-brown color. However, reddish-brown stains can also form in natural rainwater basins. Foods may have also been ground up in some basins first, then been leached. Portable grinding basins in small rock slabs that could be carried by hand are called metates, an example of which is shown on the right.
Middens are ancient garbage dumps or refuse piles. Because most contained large amounts of organic refuse, they probably were not placed too close to dwelling huts, lest they attract unwanted insects and animals. Many are identified by a rich, very dark soil that remains after the organic material in them breaks down.
Milling Stations - see Bedrock Mortars.
Petroglyphs are rock art images that are pounded or scratched on rock walls, or around bedrock mortars. More information is given under the petroglyphs heading in the Rock Art Glossary.
Pictographs are rock art images that are painted on rock walls and beneath overhangs and the ceilings of rock shelters. More information is given under the pictographs heading in the Rock Art Glossary.
Prayer Circles are circles of stones that are not associated with house pits or fire rings. Many people try to assign a religious significance to these, but no one knows for sure the purpose these rings served.
Prayer Stones are a form of petroglyph, in which isolated, or unusually-shaped or uniquely-located rocks are decorated with numerous dimples of closely-spaced cupules. There are oral traditions among many tribal groups today that some stones are sacred and have mystical properties. It follows that the finely ground rock powder made while grinding out cupules in sacred stones had mystical properties also. Hence, the origin of the name "prayer stones". Because many prayer stones sit near pictographs or petroglyphs displaying hunting scenes, and/or animals with rear tails raised to attract mates, success in hunting, or fertility, may have been properties magically contained within the decorated rocks. Wearing body paint pigments made from the powders of prayer stone cupules near decorated rocks may have been one way to release the power of these stones to imbue the wearer with certain desired abilities.
Rock Shelters are boulder caves, cavernous openings and rock overhangs that offer shelter from the weather. Some of these also contain pictographs, and most of the best rock art displays to survive the centuries are those that are so protected from the effects of rain and sunlight.



Rock Art

Binders or Binding Agents are liquids that are added to pigments to create paints. Water is an adequate binding agent that was sometimes used, but it is not as durable as other binders, and water-based paints will run if they dry out then become wet again. On the other hand, paints made with organic-based binders can darken over time, or get eaten by bugs. Plant oils worked the best for painting images on rocks, and Frank Latta (1999) writes that the oil from Wild Cucumber seeds (Marah macrocarpus), also called Chilicothe oil, was used by the Yokuts of the San Joaquin Valley, and probably by their Chumash neighbors in the mountains to the south. The seeds were chewed first to release the oils, which naturally mixed the oil with saliva. To this was then added juice squeezed from milkweed (Asclepias eriocarpa), which apparently contains an emulsifier called lecithin that makes the paint more resistant to water damage. These paints were readily absorbed by porous media, like rocks, and electrostatic forces associated with minerals in the rocks helped adere pigment to rock surfaces. However, these types of paints do not adhere well to smooth, water-tight surfaces, like skin, so grease from elk, deer or bear tallow provided the binder for body painting.
Brushes for painting designs were made from fibers extracted from crushed soaproot bulbs (genus Chlorogalum). Crayons made from semi-hard lumps of paint pigment might be used to draw designs instead of painting them with a brush.
Paint was made by combining pigment with a liquid binder. More binder made a liquid paint that was easily spread with a brush, less binder made a lump or cake of pigment that was easily carried, and which could also be used as a crayon to draw directly on a rock face.
Petroglyphs are rock art images that are pounded or scratched on rock walls, or around bedrock mortars.
Pictographs are rock art images that are painted or drawn on rock walls, and beneath overhangs and on the ceilings of rock shelters.
Pigments are colored powders that are used to make paints. This is accomplished by adding a binding agent, which is a liquid that allows the pigment to be easily spread, and helps adhere it to the medium being painted. Most pigments are first finely crushed using a stone mortar and pestle, and then heated in a red hot stone bowl to drive off impurities, break various chemical bonds, and help reduce the pigment to a fine powder.
  • Black pigments were sometimes made from charcoal, but more preferred was a crude form of graphite (pure carbon) that forms naturally in the cracks (joints) of decomposed granite bedrock buried beneath organic-rich soils. The graphite probably filtered down into the cracks when carbon from organic debris in the soil was slowly released over time, or rapidly released during a fire.
  • Blue (false blue) pigments are not "true blues", but what is known as "optical blues", or "false blues", in which a gray pigment made from charcoal mixed with gypsum looks blue when painted next to orange or red. Because red is on one end of the color spectrum, and blue is on the other, our eyes perceive the white light as blue when it reflects off the gypsum particles. Some authors believe the gypsum was made by burning clam or mussel shells, but a more likely source are flakes of naturally-occuring gypsum found in soils developed on old lake (lacustrine) deposits on the west side of the San Joaquin Valley.
  • Blue (true blue) pigments were typically made from azurite, which is a copper carbonate ore commonly found with green malachite (see below under green pigment) and is chemically similar to it. However, azurite when exposed to ultraviolet (UV) radiation from the sun eventually transforms into green malachite. Hence, some green pictographs may have originally been blue, but were altered by sun exposure. There is also mention here and there in some museum displays that ground glauconite was used as a pigment, which would have resulted in a blue-gray paint if the glauconite was used alone. However, glauconite in many places is found as blocks floating in a green matrix of serpentine, which makes it likely that chemical analyses of some green, serpentine-based pictograph paints would yield trace amounts of glauconite also.
  • Green pigments were made from the green copper carbonate ore known as malachite that is sometimes found associated with gold deposits in the Alamo Mountain area of the San Emigdio Mountains. Malachite is also found at various sites in the Southern Serra Nevadas, such as the Miners Gulch area of Mountain Home Forest, where limestone deposits are intruded by granites. A source for a different shade of green pigment is "terre verte" or "green earth", which was made by grinding up and mixing the common mineral glaucophane, which is found in blueschist, with a more rare, mica-like mineral called celadonite. Both minerals are found on the west side of the San Andreas Fault associated with some serpentine deposits.
  • Red and Brown pigments were made from hematite (Fe2O3), which is an iron oxide mineral that is called ochre (red earth) when it is found as a soil weathering product mixed with clay. It has the same basic chemical composition as rust. It differs from the yellow iron-oxide mineral limonite (yellow earth) in that no water is bound up in the hematite molecular structure, whereas limonite contains water/hydroxides.
  • Vermillion pigments were made from cinnabar, which is an ore of mercury that is found in various locations in close proximity to the San Andreas Fault.
  • White (shell) pigments were sometimes made from pulverized shells of small freshwater bivalves that are quite abundant today in the Kern River on the east side of the San Joaquin Valley, and in the now dried up lakes and marshes that characterized the east side in times past. These shells are actually mussels, though most people incorrectly call them clams, and they include the bottom-dwelling (benthic) Western Pearlshell (Margaritifera falcata) and the Western-ridged Mussel (Gonidea angulata), in addition to the floating (pelagic) mussel Anodonta californiensis. No doubt one of these made a better white pigment than the others, but we do not know which of the three worked best.
  • White (diatomite) pigments were also made from soft diatomaceous rocks (Opal A diatomite) that are found here and there on the west side of the San Joaquin Valley. Opal A diatomite is different from porcellanite, or Opal CT diatomite, which is what we use today for kitty litter. Although porcellanite tends to be more common in outcrop, it is too hard to make a good pigment. Despite the fact that Opal A diatomite closely resembles chalk, it is actually made of the opaline silica shells (test) of microscopic plants called diatoms, whereas true chalk, which is very rare in the San Joaquin Valley, is made of the calcium carbonate (CaCO3) shells of micro-organisms called forams.
  • Yellow pigments were made from the mineral limonite (FeO(OH)ĚnH2O), which is an iron oxide weathering product that is similar to the red ochre (rust/hematitie) used in red pigments, but has water/hydroxide incoporated into its molecular structure to give it a yellow color. Limonite is sometimes called "yellow ochre" or "yellow earth".


Campbell, Paul Douglas (2007), Earth Pigments and Paint of the California Indians - Meaning and Technology, Self Published, Los Angeles, California, 224 p.

Grant, Campbell (1993), Rock Paintings of the Chumash, published by the Santa Barbara Museum of Natural History and EZ nature Books, Santa Barbara, California (reprint of the original 1965 edition by the University of California Press), p. 84-87.

Latta, Frank (1999), Handbook of Yokuts Indians (50th Century Commemorative Issue), Coyote Press, Salinas, California (reprint of the original 1949 edition by Brewers Historical Press), p. 299-302 & 592-601.



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