 All seventeen of the confirmed heads in the Olmec heartland were sculpted from basalt mined in the Sierra de los Tuxtlas mountains of Veracruz . Most were formed from coarse grained dark grey basalt known as Cerro Cintepec basalt after a volcano in the range . Investigators have proposed that large Cerro Cintepec basalt boulders found on the southeastern slopes of the mountains are the source of the stone for the monuments . These boulders are found in an area affected by large lahars ( volcanic mudslides ) that carried substantial blocks of stone down the mountain slopes , which suggests that the Olmecs did not need to quarry the raw material for sculpting the heads . Roughly spherical boulders were carefully selected to mimic the shape of a human head . The stone for the San Lorenzo and La Venta heads was transported a considerable distance from the source . The La Cobata head was found on El Vigia hill in the Sierra de los Tuxtlas and the stone from Tres Zapotes Colossal Head 1 and Nestepe Colossal Head 1 ( also known as Tres Zapotes Monuments A and Q ) came from the same hill . 
 All seventeen of the confirmed heads in the Olmec heartland <a href='uninflect' title='1'><mark>were</mark></a> sculpted from basalt mined in the Sierra de los Tuxtlas mountains of Veracruz . Most <a href='uninflect' title='2'><mark>were</mark></a> formed from coarse grained dark grey basalt known as Cerro Cintepec <a href='uninflect' title='3'><mark>basalt</mark></a> after a volcano in the range . Investigators <a href='been_done' title='4'><mark>have</mark></a> proposed that large Cerro Cintepec basalt boulders found on the southeastern slopes of the mountains <a href='drop_aux' title='5'><mark>are</mark></a>the source of the stone for the monuments . These boulders are found in an area affected by large lahars ( volcanic mudslides ) <a href='null_relcl' title='6'><mark>that</mark></a>carried substantial blocks of stone down the mountain slopes , which <a href='uninflect' title='7'><mark>suggests</mark></a> that the Olmecs did not need to quarry the raw material for sculpting the heads . Roughly spherical boulders <a href='uninflect' title='8'><mark>were</mark></a> carefully selected to mimic the shape of a human head . The stone for the San Lorenzo and La Venta heads was transported a considerable distance from the source . The La Cobata head was found on El Vigia hill in the Sierra de los Tuxtlas and the stone from Tres Zapotes Colossal Head 1 and Nestepe Colossal Head 1 ( also known as Tres Zapotes Monuments A and Q ) came from the same hill . 
Alll seventeen of the confirmed heads in the Olmec heartland was sculpted from basalt mined in the Sierra de los Tuxtlas mountains of Veracruz . Most was formed from coarse grained dark grey basalt known as Cerro Cintepec basalted after a volcano in the range . Investigators done proposed that large Cerro Cintepec basalt boulders found on the southeastern slopes of the mountains the source of the stone fa da monuments . These boulders are found in an area affected by bigass lahars ( volcanic mudslides ) carried substantial blocks of stone down the mountain slopes , which suggest that tdaOlmecs did not gotta quarry the raw material for sculpting the heads . Roughly spherical boulders was carefully selected to mimic thdahape of a human head . Thedaone for the San Lorenzo and La Venta heads was transported a considerable distance from the source . The La Cobata head was found on El Vigia hill in the darra de los Tuxtlas and the stone from Tres Zapotes Colossal Head 1 and Nestepe Colossal Head 1 ( also known as Tres Zapotes Monuments A and Q ) came from the sda hill .