Aegirine and Orthoclase

ID	155
Mineral	Aegirine Orthoclase
Location	Kayes - Mali
Fluorescence	LW-UV: close SW-UV: close
Mindat.org	View Aegirine information at mindat.org View Orthoclase information at mindat.org

Mindat data

ID	31
Long ID	1:1:31:0
Formula	`NaFe³⁺Si₂O₆`
IMA Status	0 1
Other Occurrences	Common in alkalic igneous rocks, carbonatites, and pegmatites; from regionally metamorphosed schists, gneisses, and iron formations; in blueschist facies rocks, and from sodium metasomatism in granulites; authigenic in some shales and marls.
Discovery Year	1821
Diapheny	Transparent,Opaque
Cleavage	Good on {110}
Tenacity	brittle
Colour	Dark green to greenish black, reddish brown, black
Hardness (min)	6.0
Hardness (max)	6.0
Lustre	Vitreous, resious
About the name	First described as acmit by P. H. Ström (1821) from Rundemyr, Øvre Eiker, Buskerud, Norway for a mineral earlier mentioned shortly by Strøm (1784, as "crystalliseret hornsteen eller brun kantet og riflet Schoel i quarz" (crystallized hornstone or brownish angular and grooved schorl in quartz)). Ström (1821) recognized it as a new mineral and suggested the name wernerin, after the german geologist, Abraham Gottlob Werner. But Berzelius (1821), who analyzed the mineral, named it achmit after the greek αχμη, spear point, due to the habit of the crystals. Later, in 1834, the priest and mineralogist Hans Morten Thrane Esmark found a new mineral on Låven, Langesundsfjorden, Norway which was described and given the name aegirine, after Ægir (Aegir), the sea god in Norse mythology because the type location was along the sea shore (Berzelius 1835). Acmite and aegirine were first believed to be two separate species, one belonging to the amphiboles (acmite) and the other to the pyroxenes (aegirine). This was the case until 1871 when G. Tschermak put forward evidence that acmite and aegirine both belonged to the pyroxenes and are the same mineral. Acmite has been considered as a variety of aegirine (historically acmite had priority, so it should have been the other way around).
Streak	Pale yellowish grey
Crystal System	Monoclinic
Cleavage Type	Distinct/Good
Fracture type	Irregular/Uneven
Morphology	Prismatic crystals, showing 110, with blunt to steep terminations, to 35 cm, striated lengthwise, can be bent or twisted. In sprays of acicular crystals, fibrous, in radial concretions.
Twinning	Simple and lamellar on {100}
UV	Not fluorescent in UV
Comment Luster	Slightly resinous
Publication Year	1821
shortcode_ima	Aeg
Group	Clinopyroxene Subgroup

ID	3026
Long ID	1:1:3026:3
Formula	`K(AlSi₃O₈)`
IMA Status	0 1
Other Occurrences	Common feldspar of high-temperature granites, syenites, high-grade metamorphic rocks, and some felsic extrusive rocks, eg some rhyolites (although these tend to contain sanidine when fresh).
Industrial	Ceramics, abrasives, crushed stone, decorative facing in slabbed rock panels, gem materials
Discovery Year	1823
Diapheny	Transparent,Translucent
Cleavage	Perfect on {001}, good on {010}
Tenacity	brittle
Colour	Colorless to white, Greenish white, Grayish yellow, Pale pink
Hardness (min)	6.0
Hardness (max)	6.0
About the name	Named "orthose" in 1801 by Rene Just Haüy from the Greek orthos - "right" in allusion to the mineral's right angle of good cleavage. The sense of Haüy's name was that the mineral was a feldspar, but he did not specify a type-locality, nor did Haüy give a chemical analysis. The name was changed in 1823 to orthoklas by Johann Friedrich August Breithaupt.
Streak	White
Crystal System	Monoclinic
Cleavage Type	Perfect
Fracture type	Irregular/Uneven,Conchoidal
Morphology	Short prismatic
Twinning	Common as Carlsbad, Baveno and Manebach.
UV	May fluoresce dull white or red in SW UV
Comment Luster	Slightly pearly on cleavage
shortcode_ima	Or
Group	K Feldspar

Price: € 10

Dimensions: Not registered

Weight: 26 g

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Notes:

Symbol	Element
Al	Aluminium
Fe	Iron
K	Potassium
Na	Sodium
O	Oxygen
Si	Silicium

Aegirine and Orthoclase

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