*Forma,* Vol. 8 (No. 3), pp. 315-325, 1993

*Original Paper*

## Crystal Forms of Quartz and Their Changes Induced by Growth Rate Ratios of Faces, *m*, *R* and *r*

—Drawing by Computer Simulation—

Hideo Iwasaki and Fumiko Iwasaki

Sobudai-Danchi, 1-6-15-12, Sagamihara 228, Japan

(Received July 28, 1993; Accepted November 9, 1993)

**Keywords: **
Crystal Forms, Quartz, Crystal Growth, Growth Rates, Computer Simulation

**Abstract. **
Crystal forms of bi-pyramidal quartz composed of faces, *m*, *R* and *r*, were drawn by computer simulation under the specific values of growth rate ratios, 1 ² *gr*(*r*)/*gr*(*R*) ² 2 and 0 < *gr*(*m*)/*gr*(*R*) ² 2. The simulated forms could be classified into 8-groups, specified by the numerical factor, *N*, evaluated from the relation, *N* = (*R*·*r*) + *m*, where *R*, *r* and *m* expressed the number of sides in 3-kinds of faces. Values of *N* corresponding to 8-groups are specified, respectively, by 0, 3, 5, 9, 13, 21, 27 and 31. The 8-groups are regarded as the whole of possible groups in classification of crystal forms of bi-pyramidal quartz composed of faces, *m*, *R* and *r*. The comparison between drawn and observed crystal forms showed reasonable correspondence.