 All seventeen of the confirmed heads in the <unk> <unk> were sculpted from basalt mined in the Sierra de los <unk> mountains of Veracruz . Most were formed from coarse <unk> dark grey basalt known as <unk> <unk> basalt after a volcano in the range . <unk> have proposed that large <unk> <unk> 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 <unk> ( volcanic mudslides ) that carried substantial blocks of stone down the mountain slopes , which suggests that the <unk> did not need to quarry the raw material for <unk> the heads . Roughly spherical boulders were carefully selected to mimic the shape of a human head . The stone for the San Lorenzo and La <unk> heads was transported a considerable distance from the source . The La <unk> head was found on El <unk> hill in the Sierra de los <unk> and the stone from <unk> <unk> <unk> Head 1 and <unk> <unk> Head 1 ( also known as <unk> <unk> Monuments A and Q ) came from the same hill . 
