The flow of obsidian lava leads to crystal alignments that reflect both the accumulated strain and the type of flow across the surface. Microlite preferred orientations are used to investigate the emplacement dynamics, strain history, and structural evolution of Obsidian Dome, eastern California. Measurements of three-dimensional microlite trend and plunge in samples from the near-vent region, ...

Spherulites are spherical clusters of radiating crystals that occur naturally in rhyolitic obsidian. The growth of spherulites requires diffusion and uptake of crystal forming components from the host rhyolite melt or glass, and rejection of non-crystal forming components from the crystallizing region. Water concentration profiles measured by synchrotron-source Fourier transform spectroscopy re...

T he oldest representation of a physician in our country can be found at the Museo de Antropologı́a in Mexico City. It stands 9.5 cm tall and dates from 1500 BC. Little is known about surgery in our country before the appearance of the Mayan and Aztec cultures. Texoxotla-Ticitl was the surgeon of that time; he knew how to heal everyday diseases and injuries that resulted from the frequent wars. ...