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Morphogenesis of quartz crystals twinned after Japan Law

¹ Yamanashi Institute of Gemmology and Jewellery Arts, Tokoji-machi 1955–1, Kofu, 400–0808 Japan
² Ooharano Haikata-cho 452, Nishigyo-ku, Kyoto, 610–1132 Japan
³ Fujioka 1236, Fujioka-shi, Gumma Prefecture, 375–0024 Japan

^* Corresponding author, e-mail: i.sunagawa{at}nifty.com

Why quartz crystals twinned after Japan Law take flattened morphology and grow larger than the co-existing single crystals is explained based on the results of previous morphological, X-ray topographic and re-growth experimental data. It has been concluded that Japanese twin is a contact twin, and the characteristic V shape represents the upper half of a Y shape and not opposing half of an X shape. In a new locality, Japanese twins of X shape or doublet and triplet of X shapes are found, which opens a question to the validity of the above model. In this locality, unusually high proportion of quartz crystals, more than 90%, are twinned. Investigation of the samples from this locality revealed that the apparent X shape is a result of a combination of two Y shapes, indicating that the above model is valid in this case as well.

Key-words: quartz twinning, Japan Law, apparent re-entrant corner effect, contact twin vs. penetration twin, single, doublet and triplet of X-shape morphogenesis.

This article has been cited by other articles:

				K. Momma, T. Nagase, Y. Kudoh, and T. Kuribayashi Computational simulations of the structure of Japan twin boundaries in quartz European Journal of Mineralogy, April 1, 2009; 21(2): 373 - 383. [Abstract] [Full Text] [PDF]