8-Pillow lava

Ancient lava with rounded "pillow" structures formed under water. Similar "pillows" have been observed forming in modern lavas as they enter the sea or are extruded onto the seafloor. This pillow lava formed as lava flowed into a lake or shallow sea in Canada 1 to 3 billion years ago. The gray-green color is due to alteration of iron-bearing minerals in the lava, giving it the name greenstone. Note the angular clasts between lava pillows, indicating erosion and transport by waves or currents. Boulder found in glacial outwash in Brudi Stone and Gravel Co. pit, Fort Wayne.