What the author calls the "crystal interface" presents an opportunity to historicize and theorize the remarkable fascination with crystals found in contemporary art theory and practice. In aesthetics, science and art production, the crystal materializes intimations of transparency, of vitalistic transformation or of a purist stability. It powerfully articulates a line or gradation between the organic and inorganic. The author's goal is to create a context in which to understand the recourse to the crystal in contemporary art, specifically in the work of Roger Hiorns, David Altmejd and Gerard Caris. As a frame, the author examines Schopenhauer's, Worringer's and Deleuze and Guattari's adoption of the crystal as metaphor and material exemplar.