National Gem Lab

Sowcarpet, Chennai, Tamil Nadu

Mtorodite (also Mtorolite) is a trade name (marketing term) for a rare green, chromium-bearing variety of Chalcedony, named for the locality where it was discovered near the mining town of Mtoroshanga, Mashonaland West, Zimbabwe. Mtorodite, also known as Mtorolite or Chrome-Chalcedony, is a variety of Chalcedony colored by small quantities of chromium. Mtorodite is similar in appearance to the better known Chrysoprase, but differs in that Mtorodite is colored by chromium (as chromium oxide) while Chrysoprase is colored by nickel. The two can be distinguished with a Chelsea color filter, as Mtorodite (chrome Chalcedony) will appear red, and Chrysoprase will appear green. Mtorodite, unlike Chrysoprase, may also contain tiny black specks of chromite. Mtorodite, along with Agate, Carnelian, Chrysoprase, Heliotrope (blood stone), Onyx and others, are all varieties of Chalcedony which is a cryptocrystalline form of Quartz. Chrome Chalcedony from Bolivia is often called “Chiquitanita” after the Chiquitos Provnce where it is found.

Almandine is a known member of the Garnet Group of minerals that includes Almandine, Andradite, Grossular, Pyrope, Spessartine, and Uvarovite. Almandine is considered the most variety. Almandine always contains some Spessartine and Pyrope elements which create a range that is wide of including brown, red-brown, purplish red, red, purple and deep red. Almandine is the iron aluminum garnet. Pure Almandine and Pyrope that is pure are in nature and most specimens are a definite percentage for the two. Silky inclusions may be present in many Almandine gems that is only noticeable under magnification. Nevertheless, material from Idaho, United States Of America and India is recognized to contain inclusions of asbestiform minerals such as pyroxene and amphibole which create a chatoyancy that produces a star that is 4-raid.