In fact all three materials can be found in the same s.Ī variety of eye agate where the eyes are supposed to resemble the eyes of a bird.īlue colour caused by the Tyndall effect (light scattering by colloid sized particles). It is related to Minnesota silkstone and Minnesota tigers' eye. Originally described from Devon, England, UK.īinghamite refers to a diverse group of lapidary materials from the mines on the Cuyuna North Iron Range in Crow Wing County, Minnesota. Originally described from Oriente Province, Cuba.Ī name given to Chalcedony pseudomorphs after coral or shells. Jasper showing concentric red and yellow bands.Ī local name for a brown ferruginous variety of Jasper. Yellow to yellow-green chalcedony variety found in Death Valley, Inyo Co., California, USA.Īquaprase is a registered trademark of Melas, Ionannis Bloumstrom and Chordia, Avant Kumar who are marketing this material.Ī bluish green chalcedony, colored by chromium and nickel, is marketed under the trade name “Aquaprase.” Origin is an unspecif.Ĭhalcedony coloured by Chrysocolla, from Arizona, USA Layers appear darker when.Ī variety of agate consisting of Jasper veined with Chalcedony.Ī variety of agate/chalcedony replacing coral.Ī name given to a jasper found in Wabuska, Nevada.Īlso, unrelatedly, a name for a synthetic casein resin and possibly as a marketing name for gem diopside. The banding in agate is based on periodic changes in the translucency of the agate substance. Originally reported from Dirillo river (Achates river), Acate, Ragusa Province, Sicily, Italy. Used in particular for botryoidal specimens.Ī distinctly banded fibrous chalcedony. A term sometimes used for chalcedony that is not agate, jasper or another sub-variety. Aging slowly converts the mogánite into quartz and results in mogánite-free chalcedony (Moxon, 2004).Ĭhalcedony contains small amounts of water, both as molecular water and bound in silanole (Si-OH) groups (Frondel, 1982).ģ. Most chalcedony contains small amounts of the silica mineral Mogánite, usually between 1% and 20% (Heaney and Post, 1992). The more general term explained under (1) includes length-slow and length-fast chalcedony as well as microquartz. Length-fast chalcedony is far more common than quartzine.Īggregates of randomly intergrown microscopic grains are called " microquartz" (Flörke et al, 1991 Graetsch, 1994). It is not possible to distinguish the types with the naked eye. The crystallites are commonly polysynthetically twinned by the Brazil law (Graetsch, 1994 Cady et al 1998 Xu et al 1998). Length-fast chalcedony and quartzine may be found intergrown. They often show concentric banding perpendicular to the fiber orientation and are then called Agate. length-slow chalcedony or Quartzine, with crystallites stacked parallel to the c-axis, and the resulting fibers being elongated along, like in macrocrystalline quartz.īoth types tend to develop radially grown "fibers", resulting in botryoidal, rounded and stalactitic habits. The fibers may be twisted around the elongation axis.
length-fast chalcedony, with crystallites stacked perpendicular to the c-axis, and the resulting fibers being elongated either along or -more rarely - along. Based on the conspicuous behaviour of thin sections of chalcedony in polarized light, at least two types can be distinguished (Michel-Lévy and Munier-Chalmas, 1892 Correns and Nagelschmidt, 1933 Braitsch, 1957 Frondel, 1978 Flörke et al. In the strict sense, and in the scientific literature, "chalcedony" designates aggregates of parallelly grown ("fibrous") quartz crystals of microscopic and sub-microscopic size.
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