Abstract
Trapiche-like quartz, which is found in Huanggangliang area, Chifeng City, Inner Mongolia, China, has a short columnar euhedral shape. Arms of trapiche-like phenomena are formed by six radial dark bands located along the a-axis of crystals, and their cores are formed by color zones. Various methods were used to investigate the conventional gemological characteristics, trapiche pattern features, chemical compositions, and spectral characteristics of the trapiche-like quartz. CL images and EPMA results reveal they were formed at high temperature conditions and originated from pegmatite. The hexagonal darker zones with high FeO and very little TiO2 contents indicate the trapiche-like patterns are due to spatial distribution of color-inducing elements. According to the position and interpenetration relationship between inclusions, fibrous and spherical inclusions are identified as protogenetic inclusions, which were respectively identified to be ferro-actinolite and iron oxide by EPMA and Raman spectra.
Highlights
The trapiche phenomenon was first discovered in emeralds from the Muzo mining area, Columbia, where crystals were found with colorless hexagonal centers and green parts surrounding them [1]
The above analysis shows that the spherical inclusions are iron oxides, which coincide with the highest FeO content in EPMA
According to magnification and EPMA results, it can be deduced that trapiche-like patterns in quartz samples are caused by the color zones
Summary
The trapiche phenomenon was first discovered in emeralds from the Muzo mining area, Columbia, where crystals were found with colorless hexagonal centers and green parts surrounding them [1]. Kawasaki et al [28] reported a Japanese light yellow trapiche quartz, which belongs to “trapiche-type” and is caused by the formation of dendrite growth and layer growth in stages. It is obvious there are limited studies on trapiche-like quartz and their formation mechanisms are not uniform. MMaaggnniififieedd ppiiccttuurreess ooff ssaammpplleess.. ((aa)) BBllaacckk ccoorree ooff ssaammppllee qqbb11.. ((bb)) HHeexxaaggoonnaall bbaannddss ooff tthhee ttrraappiicchhee ppaatttteerrnn iinn qqbb
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