This is a Pre-Columbian VALDIVIA Stone MORTAR Plate from Ecuador, 3500 - 1800 B.C. The stone is volcanic rock. It measures about 16 3/4" X 16 3/4" X 2 3/4" ( 42.7 cm X 42.7 cm X 7.0 cm ). It weighs about 18 Lbs ( 8.2 Kgs ). The Valdivia Culture is one of the oldest in Pre-Columbian America. Originally, the pottery and ceramics were very rough because it was used for practical purposes in everyday life. The pottery was usually made of gray or red clay. As time passed by, the potters became more skilled and refined... and accomplished beautiful results. The Valdivia artisans created mortars and bowls depicting animals. What is interesting about the Valdivia Culture is that they built traditional communities in circles, surrounding a central plaza. Farming, fishing, and hunting were activities of their daily lives.