Anisotropic track etching in olivine crystals using WN solution

The olivine etchant, boiling WN solution, has been tested at three particular values of pH (7.6, 8.0 and 8.4) for various etch times up to 7 hr on externally produced fission tracks in specific crystallographic planes. Evidence has been found for systematic anisotropies in fission-track revelation in certain planes. These anisotropies reflect marked differences in the bulk etching rates for the various planes, which are found to be in the proportions 5:4:2 for the ab, bc and ac planes, respectively. Lower apparent etching efficiencies, in the range 37–77% relative to muscovite mica, have been found in some planes than would seem reasonable from critical angle considerations.