Orientation of the etch pits on a basal cut and a natural pyramid of quartz

A triangular etch pit on abasal cut of quartz, which was artificially made in dil. HF solution, is formed by three inner faces. The corner of triangle pit orientates to the left for a right handed quartz as shown in Figure 1 illustrating the arrangement of Si atoms. It can be considered from the figure that the inner face was made by the unit cell etching. The etch velocity along to the a0 axis is similar ratio to it along to the c0 axis, Thus, the Miller indices of inner face can be determined from Figure 2 as ξ[1122] by calculation of tan ρ=c0/a0 and also ρ=47°44' thereof. The orientations of etch pit on natural r and z faces are similar to the projections of basal pit on both r and z planes as Figure 3. The etch pits of left handed quartz, which are saved in the article, are enantiomorphic reversal in all figures.