Siderite and Cryolite

ID	43
Mineral	Siderite Cryolite
Location	Ivigtut cryolite deposit - Nuuk - Sermersooq - Greenland
Fluorescence	LW-UV: close SW-UV: close
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Mindat data

ID	3647
Long ID	1:1:3647:0
Formula	`Fe(CO₃)`
IMA Status	0 1
Other Occurrences	Most often found in bedded sedimentary deposits with a biological component, with shales, clays and coal beds - suggesting that the siderite is biogenically created under low-oxygen and low-Ph conditions. It is also found in metamorphosed sedimentary rocks as more massively crystalline material, as a primary gangue mineral in hydrothermal deposits, and in pegmatites, including nepheline syenite pegmatites; as bog deposits.
Industrial	An ore of iron when found in sufficient volumes to be economically recoverable.
Diapheny	Translucent
Cleavage	Perfect on {10_11}.
Tenacity	brittle
Colour	Yellowish-brown to greyish-brown, pale yellow to tannish, grey, brown, green, red, black and, rarely, colourless; tarnished iridescent at times; colourless to yellow and yellow-brown in transmitted light.
Hardness (min)	3.5
Hardness (max)	4.5
Lustre	Vitreous
About the name	Named in 1845 by Wilhelm Karl von Haidinger from the Greek "σίδηρος" (sideros), "iron", in allusion to its composition.
Streak	White
Crystal System	Trigonal
Cleavage Type	Perfect
Fracture type	Irregular/Uneven,Conchoidal
Morphology	Crystals usually rhombohedral {10_11} or {011_2}, often curved or with composite faces; also more rarely thin to thick tabular {0001}, prismatic [0001] with {11_20}, or scalenohedral; most often found as massive material, either fine-grained in sedimentary settings or massively crystalline in metamorphic settings; may also be botryoidal or globular with a fibrous internal structure.
Twinning	On {01_12}, lamellar, uncommon, with translation gliding on {0001} or {10_11}. On {0001}, rare.
shortcode_ima	Sd
Group	Calcite Group

ID	1161
Long ID	1:1:1161:3
Formula	`Na₂NaAlF₆`
IMA Status	0 1
General Appearance	Massive white transparent to translucent.
Occurrence	As a pegmatitic body in a granite stock intruded into gneiss.
Other Occurrences	Late stage mineral in granitic pegmatites, vapor phase mineral in rhyolites.
Industrial	Synthetically produced material is an important electrolyte for the production of aluminium from bauxite (Bayer and Hall–Héroult processes).
Discovery Year	1799
Diapheny	Transparent,Translucent
Tenacity	brittle
Colour	Colourless, white, brown, grey, black; colourless in transmitted light.
Hardness (min)	3.0
Hardness (max)	3.5
Lustre	Vitreous, Greasy
About the name	From the Greek κρύος, frost, and λίθος, stone, meaning "ice-stone" in allusion to its appearance.
Streak	White
Crystal System	Monoclinic
Cleavage Type	None Observed
Fracture type	Irregular/Uneven
Morphology	Crystals usually cuboidal with c, , or modified by r, v, k; also short prismatic [001]. {110} faces striated [1_11], [1_1_1], or [1_10]. Massive, coarsely granular.
Twinning	Very common. Often repeated or polysynthetic with simultaneous occurrence of several twin laws, and reflecting the pseudo-orthorhombic symmetry of the unit cell. 1. By a 90° or 270° rotation on [110], penetration, common. 2. By a 180° rotation on [110], rhombic section (11_0), repeated, less common. 3. By a 120° rotation on [021], composition surface irregular; common, especially in granular material, as fine lamellae and probably always secondary. 4. By a 180° rotation on [1_11], rhombic section near (110), repeated; rare (not in granular material). 5. On (001) or by a 180° rotation on [100], composition plane (001). 6. On (100) or by a 180° rotation on [001], composition plane (100). 7. On (112), composition plane (112). 8. On (1_12), composition plane (112). 9. On (110), composition plane (110). 10. By a 180° rotation on [111], rhombic section near (11_0). 11. On (211). (Palache et al (1951), Dana's System of Mineralogy, 7th. ed., vol. 2: 111).
Thermal Behaviour	Melting Point: 1020°. Inverts to an isometric form at about 560°. Weakly thermoluminescent.
Comment Luster	Pearly on {001}
Publication Year	1799
shortcode_ima	Crl
Group	Cryolite Subgroup

Price: € 5

Dimensions: Not registered

Weight: Not registered

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Notes:

Symbol	Element
Al	Aluminium
C	Carbon
F	Fluorine
Fe	Iron
Na	Sodium
O	Oxygen

Siderite and Cryolite

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