Topological whisker bundles of amphibole and frost column of quartz

Abstract

Amphibole whiskers showing topological forms and frost column of quartz were found in association with hedenbergite crystals in a druse of skarn at Kakino mine, Gifu Prefecture, Japan. Both selectively grow from thin layers formed on the surfaces of Fe-rich portion of early formed hedenbergite crystals. Most whiskers occur in bundles of straight, helical, coil, curl, ribbon and rope forms. Single whiskers constituting these bundles are sub-micron size in thickness and millimeter to centimeter size in length, with aspect ratio attaining more than 1000, and are twisted. Micro-area XRD analyses indicate that the whiskers are crystalline, and not in amorphous state, in spite of their topological forms. Quartz layers showing fibrous texture, closely resembling frost column in form and texture, also occur in association with hedenbergite crystals and amphibole whiskers. Both amphibole whiskers and quartz frost columns nucleated and grew in layers formed on Fe-rich portions of hedenbergite, which was selectively reacted with S, H 2O and SiO 2 containing vapor phase. Based on these observations, the growth mechanism and the genesis of such unusual morphology are discussed. Essentially similar mechanism as vapor–liquid–solid (VLS) mechanism is suggested for amphibole whiskers. The same mechanism as for the formation of ice frost column is applicable to the formation of quartz frost column.