Amethyst, Chalcedony and Calcite

ID	663
Mineral	Amethyst Chalcedony Calcite
Location	Iraí - Rio Grande Do Sul - Brazil
Fluorescence	LW-UV: close SW-UV: close
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Mindat data

ID	859
Long ID	1:1:859:4
Formula	`CaCO₃`
IMA Status	APPROVED GRANDFATHERED
Description	Calcite Group. Calcite-Rhodochrosite Series. A very common and widespread mineral with highly variable forms and colours. Calcite is best recognized by its relatively low Mohs hardness (3) and its high reactivity with even weak acids, such as vinega...
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. The yellow series exhibits blue–white fluorescence, together with a short-lived green phosphorescent afterglow after removal of the excitation source, whereas the pink series shows stable orange–red fluorescence with much weaker afterglow behavior. [[1]]
Comment Luster	Pearly on cleavage and {0001}. Can be dull or earthy in chalk variety.
shortcode_ima	Cal

ID	198
Long ID	1:1:198:0
Variety of	3337
Entry type	2
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
Lustre	Vitreous
About the name	From Greek "a-methystos", meaning "not drunk". In ancient times, it was believed that amethyst warded off drunkenness. Drinking cups were sometimes carved from amethyst. At the same time, the colour of the red wine drunk from these cups is said to have been approximately the same colour as the cups. Therefore, the wine could be diluted with water without the drinker noticing, thinking it was the material of the cup itself that warded off drunkenness.

Price: € 170

Dimensions: None mm x None mm x None mm

Weight: Not registered

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Notes:

Symbol	Element
C	Carbon
Ca	Calcium
O	Oxygen
Si	Silicium

Amethyst, Chalcedony and Calcite

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