An enormous garnet, discovered in a sewer

The finest large garnet crystal

The sewer garnet is part of the seal of the NY Mineralogical Club

I’ve just looked back at my old notes on garnets – thank goodness they didn’t all disappear, quite, with my ancient hard drive – and have been reminded of the jeweller George Frederick Kunz’s excitement in 1885 when what he estimated to be the finest large garnet crystal found to date in the United States, was found in a sewer.

“It was discovered, strange though it may seem, in the midst of the solidly-built portion of New York City” below W35th Street (between Broadway and Seventh) by a labourer who was digging for a sewer. It had not, incidentally, been lost in the sewer – garnets were evidently simply part of the bedrock of Manhattan. It was almandine, which is a nice way of saying purply-brownish, “weighed 4.4 kg, and was partly a trapezohedral shape”. Trapezohedral is the kind of description you skip over with ease, initially, thinking you know what it refers to, then in my case at least you realise you don’t have the first idea. Wikipedia describes it as ‘the dual polyhedron of an n-gonal antiprism” which didn’t help, but the illustration below is a good way to picture it. Since dubbed the “sewer garnet” it is now, apparently, part of the seal of the New York Mineralogical Society and I’m told by one of my very first blog readers (thanks!) that it can be seen at the American Museum of Natural History in New York in a place in the gallery that isn’t that obvious… so please get hunting, and let me know if you find it.

The Kunz garnet - New York Academy of Sciences Transactions 5. (1886)

You can find a few more of my random and unused notes on garnets on my new, to-be-expanded, “garnets” page here. Also, if you’re interested in the sewer garnet, the John Betts website has a good account of some of the happy and unhappy controversies and correspondences its discovery inspired.