vitrophyre - hand/display specimen of an unusual volcanic glass
Sometimes vitrophyre is described as obsidian with phenocrysts. It's not as pure a glass as obsidian, but in this case, the origin is interesting. The source of this vitrophyre was a pyroclastic flow of glowing hot volcanic ash, forming a tuff bed in the Resting Springs Formation. The ash bed was thick enough that it served as an insulating blanket for its center. The ash at the center was so hot that it melted into a glass - vitrophyre - and cooled before many crystals could form. Contrast this with an obsidian flow, where a granitic composition lava cooled so rapidly at the surface that there was no time for atoms to arrange into crystals.
On either side of this vitrophyre, the hot ash flow solidified into a densely welded tuff - vitreous instead of gritty as are many tuffs. The densely welded tuff contains fiamme or "flames" in Italian, pieces of pumice that because of the heat, melted and were squashed into almost flat glassy lense-like structures. Potassium-argon dating gives the age of the tuff and vitrophyre as 9.5 million years.
The field photo shows the layer of vitrophyre sandwiched between layers of densely welded tuff. The exposure is just east of Shoshone, California on the Charles Brown Highway.
Select a specimen: If there is more than one specimen shown, you can select a particular specimen by telling us what is in the photo with it, a black and silver pen, a black mechanical pencil, a blue and silver pen, or one of those plus some number of coins, or you can let us make the selection.
Ships by Priority Mail. Click > here < for shipping rates. Use back button to return to this page.
Making multiple purchases? Click on the "combine shipping" button in the shopping cart. We'll send an invoice with combined shipping. A link in that invoice will bring you back to checkout, no hassle.