Earth Blossoms
Chisel away with us at the science behind the “chrysanthemum stone", a 900-pound specimen bursting with white crystal “blossoms.”
By James Yang
Chisel away with us at the science behind the "chrysanthemum stone", a rock with many wonders atop its surface and still more beneath it. You can find the sedimentary rock shale in almost every region in the world, but did you know that the five-foot-tall, adult-sized specimen located in the middle of the Natural History Museum’s Unearthed: Raw Beauty exhibition is a legendary find amongst its kind? In a far-off time and place, more than 273 million years ago, a great mass of shale was forming, buried in the earth that is today’s Hunan Province in China.
Like most sedimentary rocks, the shale went through a slow and quiet process over time in its aquatic environment—it was deposited, buried by other sediments, and finally compacted into a solid rock. When you walk into the gallery, you'll notice the contrast of the dark, smooth shale next to the beautiful chrysanthemum-shaped flowers blooming on the surface.
The star of this show is in the celestine. Waters containing the elements strontium (Sr), sulfur (S), oxygen (O), and tiny amounts of barium (Ba) snaked through the inner planes and cracks of the shale, where they formed the center of the white "flowers." Coupled with pressure that ensured alignment of the planes and cracks, more fluids were pushed through the shale to pile on a little more of those same elements, and they joined the already-growing crystals to fully blossom into the pretty petals on view today.
