Abstract
ABSTRACT Topologial whiskers of metals, sulphides, selenides and nitrates showing helical or coil form have recently been synthesized by CVD methods, and attracted renewed interests as potential materials for one dimensional conductors. There have been no report in the mineral kingdom on such whiskers. This presentation reports the first observation in the mineral kingdom of 1) coiled rutile whiskers in transparent quartz, 2) amphibole whiskers showing coil, helical, curl, ribbon and rope forms formed on hedenbergite single crystals in a skarn druse, and 3) frost column of quartz formed simultaneously as 2) on hedenbergite. Rutilated quartz have been used commonly in jewelry fields and the rutile inclusions in quartz usually show needle forms, but hitherto not seriously investigated in terms of whiskers. In a polished transparent quartz sample from Myanmar, rutile whiskers showing coil form are observed together with straight or slightly twisted whiskers. Since no droplet-like particles are present at the tips of whiskers, it is considered that they are not formed by ordinary VLS mechanism, but probably formed through roughening transition of the tip surface owing to de-oxygen process due to impurity adsorption of trivalent cations. On the other hand, whiskers showing forms of coil, helical, curl, ribbon and rope selectively grown from brownish part of short prismatic hedenbergite single crystals in a druse of skarn were identified to be amphibole by micro-area XRF and micro-area XRD methods, and a seam resembling frost column as quartz. Although these whiskers show unusual topological forms, they are crystalline and not amorphous. By means of laser microscopy, it was confirmed that there are always droplet or film like substance having different compositions at the tips of amphibole whiskers, indicating that the whiskers were formed by VLS mechanism. Ribbon and curl whiskers grow from a film, and change their forms to coil, helical and rope at their tips. All these whiskers are bundles of unit whiskers with thickness less than 0.7micron, and at respective tips of unit whiskers droplet like substances are present. Topological forms are results of growth in a bundle, but individual unit whiskers show Eshelby twist. Quartz frost columns observed on the same hedenbergite single crystals together with amphibole whiskers show exactly the same features in texture, mode of occurrence and growth mechanism as ice frost columns. Both amphibole whiskers and quartz frost column were formed by a reaction between hedenbergite and vapor phase containing water and sulfur which intruded into the skarn after completion of growth of hedenbergite, followed by inclusion into later formed calcite crystals.
