Zircons and Lasers

Zircon crystals from a rhyolite tuff within the Mineral King pendant, Sierra Nevada, California. Note the scale bar in the corner to get a sense of the size of the crystals. They will be analysed using a laser ablation mass spectrometer system to determine their age through uranium-lead isotopic ratios. Image: Erik Klemetti I'll be off at Michigan State University for the next few days running some U-Pb age analyses on these zircon (above) from the Mineral King area of the Sierra Nevada in California. The grains will likely be somewhere between 98 and 220 million years old (that's why we're dating them!) Zircon are pretty distinctive when you handpick them out of a crystal separate, with that districtive pyramid end (sometimes on both ends if the crystal isn't broken), flat sides (a euhedral shape -- meaning well-formed crystal) and dark edges (an optical property due to zircon's crystal structure). ...