Calcite and Goethite

ID	549
Mineral	Calcite Goethite
Location	Rio Grande do Sul - Brazil
Fluorescence	LW-UV: check SW-UV: check
Mindat.org	View Calcite information at mindat.org View Goethite information at mindat.org

Mindat data

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

ID	1719
Long ID	1:1:1719:6
Formula	`FeO(OH)`
IMA Status	0 1
Other Occurrences	Common weathering product, primary hydrothermal mineral, bog and marine environments.
Industrial	Iron ore
Discovery Year	1806
Diapheny	Opaque
Cleavage	{010}; {100} less perfect.
Tenacity	brittle
Colour	Brownish black, yellow-brown, reddish brown
Hardness (min)	5.0
Hardness (max)	5.5
About the name	Named in 1806 by Johann Georg Lenz in honor of the German poet, novelist, playwrighter, philosopher, politician, and geoscientist Johann Wolfgang von Goethe [August 28, 1749, Frankfurt, Germany – March 22, 1832, Weimar, Germany]. Goethe was Chief Minister of State of Weimar. (Portions of the Goethe mineral collection are reputedly held by the Goethe Society in New York, New York, USA.)
Streak	Yellowish brown, orange-yellow, ocher-yellow
Crystal System	Orthorhombic
Cleavage Type	Perfect
Fracture type	Irregular/Uneven
Morphology	Prismatic [001] and striated [001]; also flattened into tablets or scales on {010}. Velvety aggregates of capillary crystals to acicular [001] and long prismatic forms often radially grouped. Massive, reniform, botryoidal, stalactitic. Bladed or columnar. Compact or fibrous concretionary nodules. Oolitic.
Twinning	Apparently none reported, but see https://www.mindat.org/mesg-631125.html and compare twinning in isostructural diaspore.
Thermal Behaviour	Heated in a closed tube, gives off water.
shortcode_ima	Gth
Group	Diaspore Group

Price: € 99

Dimensions: Not registered

Weight: Not registered

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Notes:

Symbol	Element
C	Carbon
Ca	Calcium
Fe	Iron
H	Hydrogen
O	Oxygen

Calcite and Goethite

Mindat data

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