KDP crystals have been grown from aqueous solution, and the effect of supersaturation on the induction period has been studied. The surface energy at the phase boundary separating the growing crystals from the solution has been calculated as 546 erg cm-a.
SUMMARY. Rhombohedral cleavage faces of quartz have been etched hydrothermally and with fused KOH. Stratigraphical etch patterns were observed on isolated cleavages, matched cleavage faces, and opposite sides of a thin flake. The angle between the (toii) cleavage plane and the planes responsible for the stratigraphical patterns was almost equal to the interfacial angle, 460 x 6% between adjacent rhombohedral faces. It is concluded that the stratigraphical patterns formed by preferential etching reveal the edges of weak planes deposited during growth. The implications are discussed.ETCHING is becoming an increasingly sensitive technique for revealing the sites of imperfections in crystals and studying their nature and density. Etch patterns on some crystals give information about their history and the mechanism of their growth. Such studies have been carried out by Patel et aI. (I957, 1962, 1966) and Pandya et aI. (I968), through the stratigraphical etching of cleavage surfaces of natural crystals. The present investigation reports the results of stratigraphical etching of quartz (lO~) surfaces, including single cleavages and opposite faces of a thin cleavage flake.Experimental. The present investigation was carried out on transparent single crystals of quartz, which were cleaved on (lOii) surfaces with a sharp honed chisel along a previously inscribed line parallel to the trace of a cleavage plane. Freshly cleaved surfaces, examined under the microscope before etching, revealed only the presence of cleavage lines. These cleavage surfaces were then etched hydrothermally by the method exploited by Joshi et al. (I969, 197o) for the prism and rhombohedral faces of quartz crystals. In the present work the crystals were etched in a steel bomb of internal volume 2o ml, filled with It ml of distilled water and heated to 28o ~ in a muffle furnace with temperature controlled to within ~5 ~ The crystals were etched for It hr, removed and thoroughly cleaned with conc. HNOz, water, and H20~.Fused KOH (6 g. KOH and 3 ml water) at 250 ~ was also used occasionally for etching experiments.The crystals were silvered, to enhance contrast, and the etch patterns examined under an optical microscope.Results. Fig. I illustrates a (lOil) cleavage surface after hydrothermal etching. It is interesting to note that closely spaced ridges and grooves are formed parallel to [ii21]. In addition to these patterns a large number of oriented triangular etch pits are observed in three different plane strips (which are devoid of these rectilinear patterns), 9
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.