Good to know, some of the stones may be stabilized with resin. It has been described in Gems & Gemology Journal from GIA in 1989 and in the second volume of the Photoatlas where it is written to be an oligoclase, that is not true as we will see with IR reflectance spectroscopy. They were identified as hematite and ilmenite. The inclusions are elongated and triangular mineral platelets, all oriented according to the crystal lattice directions. They are orange or brown if they are transparent and gray if they are opaque. ![]() While observed in transmitted light, inclusions' colors varies from orange, brown to gray ( figure 2). As other sunstones, it mainly has an aventurescence effect which is visible in reflected light sparkling multicolors ( figure 1). Its 'uniqueness' is its changing appearance influenced by the observator's and light's positions. The particular sunstone ( figure 1) originating from the Harts Range mountains in central Australia (Red Center) is known since 1985 but its distribution has been quite confidential. Oregon sunstone hosts microscopic copper inclusions, Tanzanian ones have rather large hematite inclusions and Indian ones show a large range of inclusions sizes. The aventurescence effect is caused by numerous inclusions reflecting light, whose the size greatly varies depending on sunstone type/origin. The sunstone is an aventurescent feldspar usually an oligoclase / labradorite (plagioclase: Ca:Na-feldspar) and more rarely an orthoclase (k-feldspar). Sunstone is well known by gemologists, especially the orange varieties from India and Tanzania, another source is Oregon in USA that produces a red sunstone.
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |