On the shores of Kamilo Point, in Hawaii, geologists have identified a new kind of stone. A sediment of recent history, the agglutinated rock displays milky-blue flecks, iotas of dull green, and fibrous orange twists. It is known, because of its unique properties, as “plastiglomerate.” That the name grinds together two familiar-sounding words is a clue to the stone’s qualities as an amalgam. What we are talking about is a rock veined not with metal or quartz, but with plastic. Plastiglomerate forms where polymer flotsam (trash, washed up on the tide line in this instance) is subject to high heat and melts, wrapping together particulate such as shell grit or sand. It then solidifies as it cools. Or, if liquefied plastic drips into hairline fissures in basalt or other porous minerals, what is left behind—a rock crazed with ersatz colors—can also be deemed plastiglomerate. Campfires are one source of that high heat. Plastiglomerate may also emerge along the scorched trail of a wildfire, or it might be cauterized into the ground by lava. It almost certainly appears in places where people burn their rubbish. Call it the birthstone of the age of unintended consequences.
Novel metals and mineraloids are everywhere today, not made by nature but engineered in the course of human industry. The bronze, brass, and pewter alloys of ancient times have been succeeded in the modern era by aluminum products (refined from bauxite), steel, industrial abrasives, synthetic gemstones, and laboratory-built crystals deployed widely in lasers. Plastiglomerate—neither natural nor fabricated, exactly—may represent the most direct conduit between our current consumer society and the far-flung future. This is how shopping enters the fossil record. Junk plastic tends to shatter or fray into filaments and specks, fine like a powder. (One of plastic’s most pernicious qualities is that it doesn’t so much decay as divide into smaller and smaller pieces.) Bonded to rock, plastic gains inertia and long-lasting cohesion; it gets gravity.