I was very excited yesterday because our dredge basket came up with pink- yes, pink!- rocks. In addition to several hundred pounds of gray, brown, and black basalt (what we usually bring up in a dredge), we brought up several dozen pebbles and cobbles which were pale to bright pink in color. I’ve attached some photographs of some representative pink rocks. When the rocks were wet in the dredge basket, the pink colors were even more vibrant, and the contrast between the dull gray rocks and the colorful pink ones even more extreme. Some of the gray basalts even have veins of bright pink. After examining these pink rocks carefully, we now think that the pink mineral is phosphorite, a mineral that precipitates from seawater similar to the way calcite does. In many of the pink rocks, the phosphorite is interspersed with white or yellow calcite crystals.
Many of the pink rocks are actually conglomerates or breccias, meaning that they are made up of smaller pieces of other rocks which have been put back together. A conglomerate consists of rounded pieces, such as stream cobbles and pebbles, while a breccia consists of more angular pieces of rock, such as rocks that have been broken up along a fault. The little pieces or clasts in our pink rocks are gray pieces of basalt and brown pieces of altered volcanic glass. These clasts are held together by the pink phosphorite, which acts like a cement. We have seen these phosphorite conglomerates and breccias before in previous dredges, but the phosphorite was always white in color. This pink phosphorite is unique, so far, in our dredges. So, what causes the pink color? I’m not completely sure. The color of a rock or mineral, especially a bright color, generally results from presence of small quantities of trace elements. Red-colored rocks and minerals are often made that color because of the presence of iron, so perhaps these phosphorites are iron-rich.
Everyone was excited by the pink rocks. I mean, who wouldn’t be after several weeks of hauling in mostly gray, brown, and white rocks? The pink rocks are great variety. I was particularly excited as the morning seemed to be full of pink. Right before the dredge basket came up out of the water, I went downstairs and put on a bright pink shirt. I bought this neon pink shirt (on sale, probably because of the bright color) to have something I wouldn’t mind destroying while handling rocks but which also had a sort of stylish flair– even out here at sea, one can be stylish in one’s own way. There were also pink strawberry muffins at breakfast and, just before the dredge came up on deck, a school of perhaps two hundred pink squid swimming around the fantail of the ship in pursuit of flying fish. I don’t believe in the supernatural, generally, but I must admit I have been wearing different colored shirts the past few days. I’ve worn a bright blue shirt, a lime green shirt, and a magenta shirt in the past two days but so far we haven’t brought up any rocks with these colors. I’ll have to try my bright orange shirt next time we dredge.
Several members of the crew and scientific party were amused by my enthusiasm over the pink dredge. I brought several samples to breakfast with me, and everyone looked at them in awe. I showed them to the captain, and we compared them with the strawberry muffins (my friend has the picture– I’ll send it later) and found a striking resemblance. You know you’re a geologist when you bring rocks to meals with you and start describing the clasts and estimating phenocryst percentages in the muffins.
In other news, the petrology crew is becoming more creative with their photos of cobbles (see attached photograph), and the captain had to play dentist one more time as I broke another bracket off my braces. Fortunately, I just broke off the bracket on my other far back molar. So, my braces are still okay, and I shouldn’t even lose any time. The captain says he’s going to start charging for my orthodonic visits if I keep breaking off my brackets. I was only eating a muffin when this one broke!
I hope all is well back home. Keep in touch!