Chalcedony, Amethyst and Calcite

ID	575
Mineral	Chalcedony Amethyst Calcite
Location	Unknown - Unknown - Unknown - Unknown
Fluorescence	LW-UV: close SW-UV: close
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Mindat data

ID	960
Long ID	1:1:960:9
IMA Status	0 1
Variety of	3337
Entry type	2
Description	Depending on the context, the term "chalcedony" has different meanings. 1. A more general term for all varieties of quartz that are made of microscopic or submicroscopic crystals, the so-called microcrystalline varieties of quartz. Examples are the ...
Other Occurrences	Very common. As nodules, vein fillings, crusts in volcanic rocks. As sinter-like crusts in low- to medium temperature hydrothermal veins. Main constituent in silica-rich marine sedimentary rocks. As nodular concretions and layers in limestones and marls. As a metasomatic replacement in limestones and marls ("replacement chert"). As cement in sandstones. Replacing other minerals in pseudomorphoses. As a fossilizing material (petrified wood, coral agate).
Diapheny	Translucent
Tenacity	brittle
Colour	colorless, white, gray, blue, any color due to embedded minerals, multicolored specimen not uncommon.
Hardness (min)	7.0
Hardness (max)	7.0
Lustre	Vitreous
About the name	Mentioned by Agricola (1546) of a stone named for the town of Chalcedon, now called Kadıköy, and is a district within the city of Istanbul, Turkey.
Streak	White
Crystal System	Trigonal
Cleavage Type	None Observed
Fracture type	Conchoidal,Sub-Conchoidal
Twinning	Quartz crystallites in the chalcedony fibers are polysynthetically twinned by the Brazil law (left- and right-handed domains).
UV	None in a pure specimen, however, green fluorescence in short-wave UV light is very common at many localities.
Comment Luster	vitreous when polished, fractured surfaces have a dull or waxy luster

ID	198
Long ID	1:1:198:0
IMA Status	0 1
Variety of	3337
Entry type	2
Description	A violet to purple variety of quartz that owes its color to gamma irradiation (Berthelot, 1906) and the presence of traces of iron built into its crystal lattice (Holden, 1925). The irradiation causes the iron Fe(+3) atoms that replace Si in the lattic...
Other Occurrences	Very common, in many different environments. The commercially most important occurrences are in volcanic rocks, where amethyst crystals outline former gas cavities. In low and medium temperature hydrothermal veins associated with iron ores. As late overgrowth ("scepter quartz") on quartz in pegmatite and alpine-type environments.
Colour	Violet - purple
Hardness (min)	7.0
Hardness (max)	7.0
Lustre	Vitreous
About the name	From Greek "a-methystos", meaning not drunk.
Crystal System	Trigonal

ID	859
Long ID	1:1:859:4
Formula	`Ca(CO₃)`
IMA Status	0 1
Other Occurrences	Found in most geologic settings and as a later forming replacement mineral in most other environments in one form or another, it is most common as massive material in limestones and marbles. It forms as chemical sedimentary deposits as limestone, can be regionally or contact metamorphosed into marbles and rarely forms igneous rocks (carbonatites). Also is a common gangue mineral in hydrothermal deposits.
Industrial	Mined extensively for a wide variety of uses ranging from lime (cement) to limestone and marble building stones and aggregates, agricultural supplements and optical calcite.
Diapheny	Transparent,Translucent
Cleavage	Perfect on {10_11}.
Tenacity	brittle
Colour	White, Yellow, Red, Orange, Blue, Green, Brown, Gray etc.
Hardness (min)	3.0
Hardness (max)	3.0
Luminescence	Fluorescent
Lustre	Vitreous
About the name	Ancient name. Named as a mineral by Gaius Plinius Secundus (Pliny the elder) in 79 from Calx, Latin for Lime.
Streak	White
Crystal System	Trigonal
Cleavage Type	Perfect
Fracture type	Conchoidal
Morphology	Over 800 different forms have been described. Most commonly as acute rhombohedrons or prismatic with scalenohedral terminations, or combinations of the two.
Twinning	At least four twin laws have been described, the most common being when the twin plane and the composition plane are {01_12}. Also common with twinning on {0001} with {0001} as the compositional surface, producing re-entrant angles. Uncommon with {10_11} or {02_21} as twin planes, producing somewhat heart-shaped crystals ("butterfly" twins).
UV	May be fluorescent under LW UV, mid-range UV or SW UV as well as under X-rays, cathode rays and even sunlight, in a number of colors and shades, commonly an intense red under SW with Mn as an activator (such as at Franklin, New Jersey, USA, and Långban in Sweden.
Comment Luster	Pearly on cleavage and {0001}. Can be dull or earthy in chalk variety.
shortcode_ima	Cal
Group	Calcite Group

Price: € 3

Dimensions: Not registered

Weight: Not registered

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Notes:

Symbol	Element
C	Carbon
Ca	Calcium
O	Oxygen
Si	Silicium

Chalcedony, Amethyst and Calcite

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