How a rock becomes a lithic.

Raw Materials

There are many types of rocks, all with slightly unique properties. Some rocks are hard and difficult to break while others are soft and easily crushed. Those rocks that do not break too easily are the best type to make tools out of. This should make sense because, you wouldn't want your hammer to break in half every time you use it. However, if you need your stone tool to be a different shape, you want to chose a rock that isn't too hard to break. Therefore, certain rocks make better kinds of stone tools than others based on its properties.

Expedient tools

An expedient stone tool is one that is made quickly and easily to preform a specific immediate task. This category includes:

• Hammerstones and Pecking Stones: These tools are usually round stones which are used for tasks such as removing the shell from a nut or shaping other stone tools. There is evidence of battering on one of more edges of a hammerstone or pecking stone which looks like little pits, often of a slightly lighter color than the rest of the rock.
• Scrapers: These tools are simply large rocks which have been broken with a few strikes of a hammerstone to make a sharp edge. A scraper can be used to remove a hide from a freshly killed animal.

Refined tools

A refined tool is one that is made to a specific shape for a task. These tools take longer to make and require more skill. This category includes:

• Projectile Points: Probably the most common example of a refined stone tool is a projectile point (arrowhead) like the one pictured above. This group of tools refers to any pointed stone tools used as a tip for a larger tools which was, by various means, thrown. Not all projectile points were used to tip arrows, some were used for spears and other weapons, therefore referring to all points as arrowpoints can lead to confusion.
• Drills: These tools are usually reworked projectile points and can look like small lithic stars with one point of the star being longer than the others. Drills were used by attaching one to the end of a stick (hafted) such that the longer point was the tip. The stick can then be placed between a persons hand and rubbed back in forth to make a drilling motion. A common use for drills was to bore holes in shells for jewelry.

Note: These are just a few examples of the many lithic artifacts that can be found. Stay tuned for a more complete listing in an upcoming Lithic Artifacts page.

How to tell if a rock is a lithic and not just a broken rock.

To make a chipped stone tool, whether it is a scraper or a projectile point, the rock the tool will be made from must be struck with another object, usually a harder rock, to cause the desired break. This simple action leaves a set of tell tale marks on the struck rock (now called a core) and on the piece of rock that has been broken off (now called a flake) which tell archaeologists that the break was intentionally made.

Understanding how archaeologists know when a piece of rock is really a lithic artifact requires just a little bit of physics. Physics tells us that the force of the blow as the core is struck with a hammerstone is greatest at the point of contact. This force then dissipates (lessens) as it travels through the rock. This dissipation is caused by the use of the force to break the rock.

What all this physics tells archaeologists is that a lithic flake will have a shape which resembles a feather, wider at one end and thinner at the opposite end. The wider end of the flake will also be thicker than the opposite end. This wider and thicker part of a flake is called the striking platform because it tells us exactly where the core was hit to create that flake.

Just below the striking platform of the flake there should be a thick rounded bump. This bump is called the bulb of percussion (a fancy way to say bump caused by the force of hitting the rock).

The bulb of percussion is important because it leaves a rounded depression in the core rock when it is made. A core rock is therefore identifiable as a lithic artifact because of the flake scars that remain on its surface. If you look closely at the picture of the projectile point at the top of this page you can seem many little depressions on it. These depressions are the result of little flakes being knocked off of the point in the process of shaping it.

Recommended Reading

1993 Making Silent Stones Speak by K.D. Schick and N. Toth, Touchstone/Simon & Schuster, NY.

Not sure of a word? Try the glossary.

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