 E. Skalwold Collection Photo: Jeff Scovil |
and Asterism Revisted | ||
| Previously unknown, the fibers are related to dumortierite and at 100-500 nm in diameter they are so small that it would take hundreds of them together to approach the thickness of a human hair. Features this small can only be imaged using a scanning electron microscope (SEM) and it was only relatively recently that their true significance became known, notably through the research of Dr. George Rossman and his graduate students, Chi Ma and Julia S. Goreva of Caltech. The cause of color in rose quartz has been debated over the years attributing it even in current texts variously to manganese, titanium, intervalence charge transfer (IVCT) between iron and titanium and to Tyndall scattering by rutile inclusions. The star effect (asterism) itself has been attributed to the rutile needles as well. |
 extracted from rose quartz. Photo courtesy of George Rossman | ||
| 1n 1987, the dumortierite-like fibers were reported by Appin and Hicks in rose quartz from the Ruby Range in Montana. Following up on this report, the Caltech team studied samples from deposits around the world, isolating the same mineral in each and quantifying its unique nature with its role in producing both the rose coloration and the asterism. Interestingly, the rose color of the fibers themselves is due to a Fe-Ti IVCT. | |||
 Click to Enlarge Single crystal pink quartz and star rose quartz. |
Rose quartz is a massive variety of quartz found worldwide in pegmatite and hydrothermal deposits. Pink quartz is a rare single crystal variety colored by radiation induced electron hole centers involving Al - P substitutions; it does not form stars. Within the massive material there are regions of single crystals which can span many centimeters (Rossman personal comm, 2008). Hense, despite its aggregate nature, the regional crystal symmetry environment allows the formation of a six ray star seen here. The quartz three-fold symmetry dictates the lining up of fibers in a plane perpendicular to its vertical c-axis and relative to the three lateral axes which are at 120 degree angles to each other. | ||
| "The focus of a star stone is not on or in the star, but above the surface - see article in Journal of Gemmology by Harold Killingback: 'Stereoscopic effect in asterism and chatoyancy' Jan/April 2005 Vol 29 No 5/6 (Alan Hodgkinson, personal communication, 2006 edit)." Currently under study and equally as facinating as the discovery of the rose quartz nanofiberous, is the discovery of nanovoids and nanorods in corundum. These appear to be the cause of asterism in corundums from certain locals.(Rossman personal comm, 2008). References | |||
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under construction Beryl Garnet Spinel | |||
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