Abstract
"Trapiche" is a word taken from a Spanish "trapicho", the gear of the sugar cane crushing apparatus. Trapiche crystals were reported on emerald, corundum (ruby and sapphire), tourmaline and spinel, which show the texture of six arms and surrounding six growth sectors resembling trapicho. We reported new trapiche-type crystal, a trapiche quartz.
Pale-yellow quartz crystals from Goyomatsu mine (contact metasomatic deposit), Nara Prefecture, Japan have the dendritic inclusion elongated parallel to the c-axis. Such a texture has never been observed in quartz crystal and is different from so-called faden quartz. In the c-cut plate, six dendritic arms in the central portion and the surrounding growth sectors are observed. A lot of voids are seen between dendrite and surrounding sectors. Electron probe micro analysis and X-ray diffraction experiments identified the central dendritic portion to be a quartz. Cathodoluminescence tomographs show the following texture. (1) The growth zoning parallel to the prism face occupied the major portion of the surrounding growth sectors, (2) the growth zoning parallel to the pyramidal faces were seen only as thin layers under the face.
These growth features indicate that the quartz crystals were formed through two growth stages: (1) Quartz dendrites grew at first under high supersaturation condition, (2) followed by changing the growth condition, the surrounding growth sectors grew under lower supersaturation condition around the quartz dendrite, which worked as seed crystals. This processes resulted in an unusual texture of quartz crystals, a trapiche quartz.
