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Photo of Curtis Runnels Curtis Runnels as seen on Mediterranean On the Rocks: The Paper Boat

Click on Curtis's photo to read a brief bio.

q What happens to the tools you find. Do they go to a museum? (Question from Sherry)

A All of the artifacts from the Franchthi Cave excavations are stored in the Archaeological Museum in Nafplion, Greece. Some of the more interesting pieces are on display. Greek antiquities legislation of long standing requires that cultural materials of any description are the property of the Greek state and must remain within the country.

q What different kinds of tools were made from obsidian? (Question from 6th grade science students, Augusta, GA)

A Dozens of retouched (secondary chipping to modify the shape of working edges) tools were manufactured by the prehistoric inhabitants of the cave. Arrowheads, blades for insertion into sickles for cutting plants, piercing and cutting tools, and many other tools were useful for the foragers and farmers who occupied Franchthi Cave from the Palaeolithic period (nearly 30,000 years ago) to the end of the Neolithic period about 5000 years ago.

q Have you been able to figure out how all the tools you found were used? (Question from David)

A No. Expert analysis (by my colleague Patrick Vaughan) of the working edges of tools with a microscope was attempted, but the coarse scratchy particles in the sediments in which they were buried made such analysis very difficult. In the end it was not possible to make many identifications. The best luck came with the sickle elements (the blades inserted in wooden or bone handles for cutting plants). Vaughan and Catherine Perles found that flakes and blades of flint and obsidian frequently had a deposit or polish on the edges, as do modern sickles, that evidently results from the deposit on the tool's edges of silica from the cell walls of the plants that are being cut as the result of heat generated by friction.

q How is obsidian formed? Is it always deposited during volcanic activity? (Question sent by Brooke, 6th Grader, St. Paul's School, Clearwater, Florida)

A Obsidian is a natural form of glass. Obsidian is formed during volcanic activity when lava, with the right chemical composition (high in acid), cools very quickly upon contact with the atmosphere during an eruption. The rapid cooling prevents the formation of the distinct crystals you often see in volcanic rocks. If it cooled slowly, allowing the crystals to form, it would be classed usually as dacite or rhyolite. Most obsidian is black, but there are red and green varieties as well. Obsidian is found in the Aegean Sea on the island of Melos and one or two other places. In the west Mediterranean it is found on Lipari island among other places. Obsidian is also found in Turkey, Hungary, Ethiopia, and many other countries. In the United States obsidian is found in Yellowstone National Park and in the Pacific mountain ranges of California and Oregon.

q About how long does it take to make to a tool like the hand axe Alan Alda was making on the show? (Question sent by Alex)

A That is a good question, Alex. Alan Alda turned out to be a very good flintknapper (someone who makes stone tools). I have taught people how to flintknapp for 20 years and I have learned that it can take a while for someone to learn how to do it. Alan Alda picked it up right away and he made his handaxe in about half an hour. A practiced flintknapper can make a handaxe out of flint or obsidian in about 10 or 15 minutes on average. Stone tools did not take long to make, and they break, wear out, or get dull very quickly. Fortunately, the raw materials are easily found and many tools can be made in a short period of time. Skilled flintknappers in England or Turkey in the 19th century could make up to 5,000 flakes or blades suitable for toolmaking in a single day! This is why archaeologists find so many stone tools on prehistoric sites (more than 1,000,000 were found at Franchthi Cave in a very limited area of excavation).

q Has obsidian been used for other things besides tools throughout the ages? (Question asked by several viewers)

A Obsidian has been used for bowls in the prehistoric Near East over five thousand years ago, as inlays for ceramic sculpture in Neolithic Turkey (for instance at Hacilar), as mirrors (at Catal Hoyuk, also in Turkey), and as part of sculptures made by groups as different as the Minoans of ancient Crete (they carved obsidian in the form of shells) and the ancient Maya and Aztecs of Mesoamerica who used obsidian to form the eyes, or at least the pupils, of jade masks. These uses, however, are very rare. Obsidian is brittle but very hard. It is difficult to work obsidian, which must be flaked and then ground with emery or other hard abrasives, into rounded forms. The very sharp edges of the flakes and blades struck from obsidian cores as depicted in the film have very sharp edges that lend themselves to use for cutting tools and weapons. The most spectacular use for obsidian in my opinion was by the Aztecs (Mexica) of ancient Mexico who used obsidian blades set in grooves in wooden handles to make deadly swords called "macuahuitl".


Scientific American Frontiers
Fall 1990 to Spring 2000
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