Dear Colleagues, I've recently encountered some analytical problems when running siderites. Does anyone have a calibrated siderite that they run as an internal standard to check analytical performance when measuring the isotopic composition of siderite-bearing samples? Is so, could you spare a small amount (~100mg) so that I can check the accuracy of our analytical procedures? Regards, Steve Crowley Department of Earth & Ocean Sciences Herdman Building University of Liverpool 4 Brownlow Street Liverpool L69 3GP UK