Basaltic rocks are rocks made from a volcanic material called basalt. They are dark in color and are formed when lava cools down quickly on the Earth's surface. Full definition
The maria are solidified lava flows, vast outpourings of basaltic rock from around three and a half billion years ago. (discovermagazine.com)
The researchers injected this bubbly liquid into basaltic rock some 400 to 800 meters (about 1,300 to 2,600 feet) below ground. (sciencenewsforstudents.org)
This means that columnar joints exposed in basaltic rocks, as observed at the Giant's Causeway and Devils Postpile (USA) amongst others, were formed around 840 - 890? (sciencedaily.com)