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Ground stone

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Ground stone refers to a specific category of stone tools. These tools are formed through the process of grinding. This can happen on purpose or by accident. People often use coarse-grained stones to process other materials. These materials can be organic, like plants, or inorganic. Ground stones are found all over the world. They are sometimes the only artifacts left at archaeological sites.

Molino neolítico de vaivén
Molino neolítico de vaivén

Creating these tools requires a very specific process. First, a maker must choose a tough stone. A good stone must withstand hard impacts without flaking or cracking. If a stone breaks easily, the work is wasted. Makers often choose igneous or cryptocrystalline rocks. Cryptocrystalline rocks have a very fine grain structure. These small grains make the rock much harder.

Néolithique 0001
Néolithique 0001

There are several ways to shape these stones. To drill a hole, a person might use a sharp, pointed stone. They can also use a hardened stick. By spinning the point with hand pressure, a hole forms. Adding sand to the hole helps grind the stone away faster. To make a hole go all the way through, the maker drills halfway from one side. Then, they finish the hole from the opposite side.

Some tools are made through labor-intensive manufacturing. For example, axes and adzes are made by repeated grinding. Makers often use a harder stone or sand as an abrasive. Water is sometimes used as a lubricant during this process. Other tools, like manos, are considered incidental. Manos are hand stones used with a grinding slab called a metate. They develop their ground surfaces through constant wear during use.

Ground stone technology is linked to the Neolithic period. This era is also known as the New Stone Age. The three-age system was developed by Christian Jürgensen Thomsen. In the Levant, ground stones appeared during the Natufian period. In prehistoric Japan, they appeared during the Paleolithic era. This may have happened 25,000 years before it happened elsewhere.

Grinding stone
Grinding stone

These tools served many different roles in society. Some were used for heavy work, like axe heads. Makers would grind notches into the stone for hafting. This allowed the stone to be tied to a handle with hide. Others were used for food and medicine. A mortar is a stone bowl used for mashing. A pestle is the heavy tool used to press into it.

MortarandPestle
MortarandPestle

This pair is used to turn seeds into powder. Some ground stones were even used as jewelry. Items like beads or ear spools showed high status. This is because they required so much time and detail to make.

Archaeologists use special methods to study these objects. They want to understand ancient agriculture and domestication. One method is use-wear analysis. This looks at the traces left by pounding, grinding, or cutting. Scientists also look for botanical remains. These are tiny starch grains and phytoliths. These remains get trapped in the micro-crevices of the stone.

Grinding stone
Grinding stone

Researchers use an ultrasonic bath to extract these traces. Then, they observe them under a polarized microscope. This helps them identify exactly which plants were processed.

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🖼️ Images & Media (4)
File:Néolithique 0001.jpg
Néolithique 0001.jpg
File:Molino neolítico de vaivén.jpg
Molino neolítico de vaivén.jpg
File:Grinding stone.jpg
Grinding stone.jpg
File:MortarandPestle.jpg
MortarandPestle.jpg
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