Motza Archaeological Site, on the western edge of Jerusalem
Long before pottery and thousands of years before the Romans, Neolithic communities near Jerusalem mastered a sophisticated technique for transforming local rock into strong mortar, revealing an unexpected level of prehistoric engineering.
Researchers have discovered new evidence that Neolithic populations in the Judean Hills reached a engineering advancement 8,000 years before the ancient Romans started using it.
The ancient technology, now thought to have been invented nearly 10,000 years ago based on discoveries made at the archaeological site of Motza near the western edge of Jerusalem, consisted of burn limestone and dolomite places to produce a form of much more resistant mortar than other known varieties from the same time, which were composed mainly of calcite.
But according to one now published in Journal of Archaeological Sciencelong before the use of ceramics, ancient neolithic inhabitants of Motza they had already discovered pyrogenic dolomite mortar and were using this surprisingly sophisticated engineering skill to construct mortar floors and other fixed elements.
One of the main ingredients of mortar is calcitea whitish mineral composed of calcium carbonate derived from limestone.
However, during the Neolithic, in the area of current Motza, these first engineers apparently they already used not only limestone to produce mortarthat of its floors, but also dolomite existing in the region.
This is significant because the resulting fumed dolomite mortar would inherit the properties of dolomite stone, making it much harder and more water resistant, explains .
A oldest written source known reference to these processes appears in the texts of the Roman architect and military engineer Vitruviuswho in the 1st century BC wrote about two types of rock used in the production of lime: a light stone, limestone, and another hard stone, which most experts believe corresponds to dolomite.
Due to this reference, it was long believed that engineers Romans had been the first to use dolomitic lime in this way — a far from simple task, which requires a level of technical knowledge in practically all phases of production and which would have seemed inconceivable to Neolithic builders — until now.
Even in modern examples of dolomitic lime, as well as in historical examples known to archaeologists, magnesium-containing lime generally does not recombine with calcite-based lime to form dolomite. Instead, known examples show the formation of several minerals rich in magnesiumalong with a number of other amorphous secondary compounds.
According to the authors of the new study, “surprisingly, the Motza dolomitic mortars mainly contain dolomite and calcitebut the properties of dolomite support its identification as pyrogenic dolomite, which re-formed after decarbonation in the mortar production process.”
To determine whether Motza’s examples were, in fact, pyrogenic dolomiteresearchers carried out analytical tests on remains of mortar ovens and on pavements from archaeological sites in the region.
The combination of these tests with studies of experimental recreations that imitated the supposed technique of Neolithic artisans in the region, and with modern technologies such as scanning electron microscopy and optical microscopy, led to a surprising discovery.
“The results suggest a technology lost to historywhich allowed a complete cycle of dolomitic lime, similar to the known calcitic lime cycle”, report the study authors.
According to researchers, the ancient inhabitants of Motza, in the pre-ceramic Neolithic, followed a traditional method of mortar productionbut with a important difference: they adapted conventional recipes that normally used lime or gypsum and started to use local materials available at the time.
By accident or trial and errorthe ancient inhabitants of Motza managed to perfect the use of dolomite under these conditions, “despite the technical difficulties”.
As for concrete way in which this was achievedthe authors of the new study suggest that “they could have successfully produced a dolomitic mortar in which the dolomite completely recrystallized together with the calcite,” something that, they emphasize, “as far as we know, has not been observed anywhere elser”.
