The boulders were transported over 150 kilometres (93mi) from the source of the stone.
 Most were formed from coarse grained dark grey basalt known as Cerro Cintepec basalt after a volcano in the range.
It is possible that this damage was caused by the initial stages of re-carving the monument into a colossal head but that the work was never completed.
Earth structures such as mounds, platforms and causeways upon the plateau demonstrate that the Olmec possessed the necessary knowledge and could commit the resources to build large-scale earthworks.
The backs of the heads are often flat, as if the monuments were originally placed against a wall.
The period of production of the colossal heads is therefore unknown, as is whether it spanned a century or a millennium.
The heads were variously arranged in lines or groups at major Olmec centres, but the method and logistics used to transport the stone to these sites remain unclear.
However, the San Lorenzo heads were buried by 900BC, indicating that their period of manufacture and use was earlier still.
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