Prehnite

Prehnite, Epidote
General
Category Silicate mineral
Chemical formula Ca2Al(AlSi3O10)(OH)2
Identification
Color Colorless to gray to yellow, yellow-green or white
Crystal habit Globular, reniform to stalactitic
Crystal system Orthorhombic - Pyramidal (mm2)
Twinning Fine lamellar
Cleavage Distinct on [001]
Tenacity Brittle
Mohs scale hardness 6 - 6.5
Luster Vitreous - pearly
Diaphaneity Semi-transparent to translucent
Specific gravity 2.8 - 2.95
Optical properties Biaxial (+)
Refractive index nα = 1.611 - 1.632 nβ = 1.615 - 1.642 nγ = 1.632 - 1.665
Birefringence δ = 0.021 - 0.033
Dispersion weak r > v
Ultraviolet fluorescence Fluorescent, Short UV=blue white mild peach, Long UV=yellow.
References [1][2][3][4]

Prehnite is a phyllosilicate of calcium and aluminium with the formula: Ca2Al(AlSi3O10)(OH)2. Limited Fe3+ substitutes for aluminium in the structure. Prehnite crystallizes in the orthorhombic crystal system, and most oftens forms as stalactitic or botryoidal aggregates, with only just the crests of small crystals showing any faces, which are almost always curved or composite. Very rarely will it form distinct, well individualized crystals showing a square-like cross-section, like those found at the Jeffrey Mine in Asbestos, Quebec, Canada. It is brittle with an uneven fracture and a vitreous to pearly lustre. Its hardness is 6-6.5, its specific gravity is 2.80-2.90 and its color varies from light green to yellow, but also colorless, blue or white. In April 2000, a rare orange Prehnite was discovered at the famous Kalahari Manganese Fields in South Africa. It is mostly translucent, and rarely transparent.

Though not a zeolite, it is found associated with minerals such as datolite, calcite, apophyllite, stilbite, laumontite, heulandite etc. in veins and cavities of basaltic rocks, sometimes in granites, syenites, or gneisses. It is an indicator mineral of the prehnite-pumpellyite metamorphic facies. It is the first mineral to be named after someone, and was first described in 1789 for an occurrence in Haslach, Harzburg and Oberstein, Germany, and named for Colonel Hendrik Von Prehn (1733–1785),[1] commander of the military forces of the Dutch colony at the Cape of Good Hope from 1768 to 1780. Extensive deposits of gem quality Prehnite occur in the basalt tableland surrounding Wave Hill Station in the central Northern Territory, of Australia.

Gallery [link]

  • Emerald cut Prehnite, 1.85 cm x 1.42 cm, 4.6 grams.

  • Carved yellow Prehnite pendant, 2.4 cm x 1.8 cm, 5.5 grams.

  • Botryoidal Prehnite fragment, 12.0cm x 11.0cm, 646 grams.

  • Prehnite nodule fragment, 11.0cm x 7.0cm, 338 grams.

  • Sliced Prehnite fragment with calcite core, 9.0 cm diameter.

  • Prehnite, New Haven Co. CT, USA

See also [link]

References [link]

  1. ^ a b https://webmineral.com/data/Prehnite.shtml Webmineral data
  2. ^ https://www.mindat.org/min-3277.html Mindat
  3. ^ Hurlbut, Cornelius S.; Klein, Cornelis, 1985, Manual of Mineralogy, 20th ed., ISBN 0-471-80580-7
  4. ^ https://rruff.geo.arizona.edu/doclib/hom/prehnite.pdf Handbook of Mineralogy
Wikimedia Commons has media related to: Prehnite

https://wn.com/Prehnite

Podcasts:

Email this Page Play all in Full Screen Show More Related Videos
PLAYLIST TIME:

Who Is She 2 U (Remix)

by: Brandy

C'mon. Watch this. Uh, uh, uh, uh. C'mon. G-G-Get on down. This that soul bounce right here. G-Get on down. B-Rocka...
Usher... Usher... Usher... Uh, uh, uh. What we bout to do. A-Just get on down. Brandy...
Don't even think about calling me crazy. You know you peeped that lady (Yeah, yeah yeah. Yeah Yeah). Then when I turned
and looked at you, you tried to play it off. But I could tell that you 2 were friends.
She was just too nervous. And she was looking like she was hurt. Like a memory had surfaed. It kinda got her pissed. I'm
kinda wondering myself and you're really no help to me. How you 2 know each other so well? Cause I wanna know now. You
better start talking...
Who is she to you? Don't lie to me. Who is she to you? My eyes can see. There's something going on between you 2. I think
you better let me know, that's fa sure.
Who is she to me? Nobody babe. Who is she to me? No need to explain. I ain't done nothing wrong. I swear to you. Ain't
nothing going on but us. That's wassup.
See I don't know why homegirl keeps on lying on everything. I'm not lying (No, no, no. Oh no. No, no, no, no). You make
it worse acting all insecure. She see you bugging so that's why she wants to be spotted, yeah.
Go 'head and say you don't try trust me (trust me)! Always going outta your way to bust me! You come up empty-handed. You
don't understand it. You better go 'head and listen! Girl you got it twisted. Don't be paying that broad no attention.
Cause the one I'm with. Don't be asking me... Yeah...
Who is she to you? Don't lie to me (Who is she). Who is she to you? My eyes can see (My eyes). There's something going on
between you 2. I think you better let me know, that's fa sure.
Who is she to me? Nobody babe. Who is she to me? No need to explain. I ain't done nothing wrong. I swear to you. Ain't
nothing going on but us. That's wassup.
Damn right, I wanna know her name (Why?) Tell me how you know her babe (I don't). Why did you make that face? You look so
ashamed.
I'm not ashamed, I'm surprised you think of me as that guy. I've never done you wrong. What's going on! I don't know who
she is.
Who is she to you? (Who is she) Don't lie to me. Who is she to you? (What did you do) My eyes can see. There's something
going on between you 2. I think you better let me know, that's fa sure.
Who is she to me? Nobody babe (This is crazy...). Who is she to me? (..To think I'd cheat on my baby) No need to explain.
I ain't done nothing wrong. I swear to you. Ain't nothing going on but us. That's wassup.
Who is she to you? Don't lie to me (Don't lie). Who is she to you? My eyes can see (Tell me the truth). There's something
going on between you 2. I think you better let me know, that's fa sure.
Who is she to me? Nobody babe (Nobody baby). Who is she to me? No need to explain (No need to explain). I ain't done
nothing wrong. I swear to you. Ain't nothing going on but us. That's wassup.
Get on down. Get on down. C'mon.
Timbo... We gon get on down. We gon get on down.
B-Rocka... We gon get on down. We gon get on down.
Timbo the King. Brandy the Queen.




×
×
×
×