Several types of Garnets with optical phenomena are understood. They include color-change, pet’s eye, star and hardly ever, iridescent Garnet. Colors change Garnets are usually Pyrope-Spessartine, while star Garnets are usually Almandine or Pyrope-Almandine. Iridescent or “Rainbow” Garnet is a very variety that is unique of or Grossular-Andradite (also called “Grandite”) Garnet. Specimens of iridescent Garnet had been first collected in 1934 at the Adelaide mining district, Nevada, USA. Early studies of those samples proposed the iridescence was due to twinning that is regular the crystal surfaces but later on, more in-depth research did not show any proof of twinning.
Rainbow Garnet has additionally been found in Mexico at a mine found about 200 kilometres southeast of Hermosillo in Sonora, Mexico. This is the source that is mainly of Garnet before the discovery in Japan in 2004. Rainbow Garnet from Japan was first found in very early 2004 by several sets of mineral collectors near the Kouse that is old Magnetite in the Tonkawa area of Nara Prefecture located around 60 km southeast of Osaka. The Garnets found here are not quality that has lots of September 2004 a local mineral collector named J. Sugimori found an outcrop gem-quality that is containing strongly iridescent and relatively clean Andradite Garnet crystals. Over the following four months, he used hand tools to proceed with the vein to a level of 5 m. Several hundred kilograms of well-formed Rainbow Garnet crystals showing iridescence that is spectacularly recovered. Apart that is small of material could possibly be considered gem quality. In August 2005, regional authorities from Tenkawa village prohibited Garnet that is additional recovery the area. This source happens to be closed and off-limits and mostly overgrown by forest. Collecting only at that location is strictly prohibited and field collectors were arrested.
The Rainbow Garnet from this location does occur as reasonably small crystals with an orangy brown body color but exhibit many different iridescent colors with regards to the viewing orientation while the particular face that is crystal. The sensation varies from a color that is single a range of colors that shifts as the gem is rotated. Some crystal faces can also display a spectrum that is filled with or a “rainbow” of colors. The crystals from this location are nearly Andradite that is purely determined by their chemical composition. The microscopic assessment shows the existence of a rather complex lamellar, or thin-layered, structure. These alternating, microscopic layers are of the slight structure that is different varying widths. Some layers are nearly Andradite that is pure is Andradite with a Grossular component. These layers that are microscopic formed by crystal intergrowth, distortion and possibly twinning. This structure that is complex in charge of the iridescent colors by diffraction of light through and bouncing off of the many microscopic layers. (GIA Gems & Gemology, Winter 2006)
Rainbow Garnet crystals are beautiful and popular but gems that are faceted really rare. This is as a result of the thin layers of iridescence being so close to the area of the crystal. Polishing of facets too profoundly will polish the iridescence next to. Also, just a very percentage that is little of crystals are facetable. Many crystals are entirely opaque. A gem that is translucent necessarily be tiny. A gem with nice translucency and symmetry is quite rare. The gem pictured above is just an unusual and beautiful example of a tiny, translucent gem with excellent rainbow iridescence. Due to the fact gem is rotated the many facets light up with the rainbow flash that is iridescent.
|Calcium iron silicate|
|Transparency:||Semitransluscent To Opaque|
|Lustre:||Subadamantine To Vitreous|
|Fracture:||Conchoidal To Uneven|
|Cleavage:||None May Show Indistinct Parting|
|Dispersion:||Strength: strong fire Value: 0.057|