It often isn't easy to tell of a geological object is natural or has been
modified by the hand of humans.
Artifacts are discrete objects which bear some modification from the
natural state attributable to humans.
One of the first and basic tasks of archaeology is that of differentiating
such human-modified materials from materials that are unaltered from their
natural state Alteration may take several forms, resulting in
archaeological materials of differing character.
Natural objects may be purposefully modified or moved by man to
serve some end. Tools, utensils, and weapons are familiar artifacts of
Natural objects may become modified in physical form as the
incidental result of use. The worn surface of a cobble pestle or the
dulling of the sharp edge of a stone flake used as a knife represent
examples of modification of this kind
The processes of manufacture, preparation or use may result in
waste materials which may not be used further but which nevertheless
reveal human activity . Flakes removed in shaping a stone tool, the
discarded shells of seeds ground for food, the ash remaining from a
log burned for heat all represent this form of modification (There is
no unanimity in referring to all such materials as artifacts . The
term "ecofact" is sometimes used to refer to faunal, floral, or
geological specimens modified by human in an ecological context but
which lack modification of the first two forms)
Objects may be modified with respect to provenience with or without
modification of physical form . This kind of modification is
represented by, for example, an otherwise unmodified quartz crystal
found in a dead shaman's ceremonial pouch or a river cobble located on
a ridge top You will note that specimens of this last kind are
identified as artifacts from association or contextual data . This
discussion does not consider artifacts of this kind further except to
say that their recognition as artifacts requires knowledge of their
natural provenience and sensitivity to their spatial relationship to
other more readily recognized evidence of human behavior
For several reasons the identification of stone artifacts will pose
problems These reasons include the circumstance that many stone artifacts
are minimally shaped, the fact that primitive ways of working stone
involve processes closely replicated in nature, and the general lack of
knowledge concerning the properties of stone and the methods whereby it is
worked by humans.
As a first prerequisite, then, it is necessary to become familiar with the
nature of stone and the technology of working it. Different types of
stones have different properties. Aside from its widespread availability,
properties which attracted humans to stone include...
Density, which lends itself to use as hammer stones or weights
(basalt, quartzite, hornfels)
Brittleness, resulting in sharp fractured edges usable for cutting
or piercing (obsidian, flint, chert, quartz)
Abrasiveness, which serves well in grinding functions ( sandstone,
Softness, providing for ease in shaping without hard tools (shale,
Aesthetic beauty in coloration or texture, and/or rarity, inviting
use as articles of adornment or status (quartz, topaz)
Common abraided stone artifacts
If a stone specimen shows no flake scars, examine it carefully for pecking
or grinding marks . Pecking may show up on an otherwise smooth cobble as
small, shallow, light-colored pits where the rock was hit with another
rock or where it was used to hit another piece . These marks are most
likely to occur along or toward edges, but may also occur toward the
Pecking is chipping the rock from the middle towards the edge and is less
precise than flaking
Grinding and polishing are not always easy to detect because smoothing of
the rock surface can and does occur through nature weathering.
Be on the lookout for the following kinds of clues shoulder:
Evidence of shoulders
Profile shows angle or shoulder where curvature of new surface intersects
the original outline
Shoulder (edge) on pestle where rock has been removed
Sharp edge pits
On vesicular rock, the new surface makes sharp angle with exposed vesicles
In naturally weathered surfaces exposed vesicles will have rounded edges
pit edges rounded
If grinding occurs on an uneven, undulating surface, polish will occur
mainly on the high spots even polish
Smooth curved ground surfaces
In a stone tool curved surfaces will be smooth with no protuberances.
The presence of a protrusion on either a convex or concave surface usually
indicates that the surface was not used for grinding.
Grinding through grains
Ground stone tools will show evidence (in crossection) of grinding through
grains - this evidence may be microscopic.
In granular or large grained rock, grinding will cut through individual
grains to form a smooth surface ; in natural smoothing, this is less
likely to occur . (This may not be observable without the use of a lens)
Step by step procedure for determining intentional grinding...
First, feel the clean specimen all over with the fingers for
differences in surface texture and sharpness of exposed edges .
Second, hold the specimen up to a strong light and examine it from
different angles to see if there are any differences in reflectance .
Examine the specimen by eye, or better yet, with magnifying glass or
microscope for striations, looking especially for those that are not
randomly distributed but form patterns oriented to the outer borders
or along the longitudinal axis .
Hold a straight edge to the surface and observe its contours Most
intentionally ground surfaces are either flat or slightly and evenly
cured in a convex or concave arc; undulating surfaces should warn