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Very Hot Topic (More than 25 Replies) Lazulite - January 2015 (Read 16206 times)
Scott LaBorde
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Lazulite - January 2015
Jan 2nd, 2015 at 10:43am
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Lazulite ((Mg,Fe2+)Al2(PO4)2(OH)2) is a blue, phosphate mineral containing magnesium, iron, and aluminium phosphate. Lazulite forms one endmember of a solid solution series with the darker iron rich scorzalite.

Lazulite crystallizes in the monoclinic system. Crystal habits include steep bipyramidal or wedge-shaped crystals. Lazulite has a Mohs hardness of 5.5 to 6 and a specific gravity of 3.0 to 3.1. It is infusible and insoluble.

It forms by high grade metamorphism of high silica quartz rich rocks and in pegmatites. It occurs in association with quartz, andalusite, rutile, kyanite, corundum, muscovite, pyrophyllite, dumortierite, wagnerite, svanbergite and berlinite in metamorphic terrains; and with albite, quartz, muscovite, tourmaline and beryl in pegmatites. It may be confused with lazurite, lapis lazuli or azurite.

It is found in Salzburg, Austria; Zermatt, Switzerland; Minas Gerais, Brazil; Lincoln County, Georgia; Inyo County, California; the Yukon in Canada, and elsewhere.

It was first described in 1795 for deposits in Styria, Austria. Its name comes from the German lazurstein, for blue stone or from the Arabic for heaven.


CategoryPhosphate mineral
Formula
(repeating unit)
(Mg,Fe2+)Al2(PO4)2(OH)2
Strunz classification08.BB.40
Crystal symmetrysymmetry      Monoclinic prismatic
H-M symbol: (2/m)
Space group: P 21/c
Unit cella = 7.144(1) Å, b = 7.278(1) Å, c = 7.228(1) Å; β = 120.5(1)°; Z=2
ColorAzure-blue, sky-blue, bluish white, yellow-green, blue-green, rarely green
Crystal habitTabular, acute to stubby bipyramidal crystals; granular, massive
Crystal systemMonoclinic
TwinningCommon by several twin laws
CleavagePoor to good on {110}, indistinct on {101}
FractureUneven, splintery
TenacityBrittle
Mohs scale hardness5.5 - 6.0
LusterVitreous
StreakWhite
DiaphaneityTransparent to translucent to nearly opaque
Specific gravity3.122 – 3.240
Optical propertiesBiaxial (-)
Refractive indexnα = 1.604 - 1.626 nβ = 1.626 - 1.654 nγ = 1.637 - 1.663
Birefringenceδ = 0.033 - 0.037
PleochroismStrong: X= colorless, Y= blue, Z= darker blue
2V angleMeasured: 61° to 70°
FusibilityInfusible
SolubilityInsoluble


Wikipedia source:  http://en.wikipedia.org/wiki/Lazulite
  

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Timh
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Re: Lazulite - January 2015
Reply #1 - Jan 2nd, 2015 at 11:06pm
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Here's a piece I collected in Gaston Co. N.C.
  

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Dennis
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Re: Lazulite - January 2015
Reply #2 - Jan 3rd, 2015 at 10:05am
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Nice specimen, Tim

Here's a piece I was happy to get last year.  It's from the classic Clubb Mountain Kyanite Prospects (Chubb Mountain Kyanite Prospects) in Gaston Co. (#1026, ex. David M. Crawford collection).  The matrix consists of small kyanite crystals.

Dennis




  

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Re: Lazulite - January 2015
Reply #3 - Jan 3rd, 2015 at 9:31pm
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Yours is very nice as well Dennis. I have never been quite sure just exactly where the Clubb /Chubb Mtn. site actually is. However I know the general area it is in and my piece came from that area as well. I also collected some of the kyanite and rutile. The geology there appears to be very similar to Graves Mtn in Georgia.
  
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Laurie Adams
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Re: Lazulite - January 2015
Reply #4 - Jan 4th, 2015 at 8:20pm
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Nice specimens Dennis and Tim.  In addition to the Chubb Mountain occurrence, Lazulite has also been found in North Carolina at Crowders Mountain in Gaston County, Cotton Stone Mountain in Montgomery County, the Staley (Carolina) Pyrophyllite Mine in Randolph County, the Cabin Creek Pyrophyllite Mine in Moore County, the Piedmont Minerals Mine in Hillsborough in Orange County.  If anyone knows of other NC sites, please let us know.  Notice that all of these sites are high temperature alumina deposits, and as Tim said, very similar to Graves Mountain in Georgia.
  
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Re: Lazulite - January 2015
Reply #5 - Jan 14th, 2015 at 10:21am
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The best lazulite that I have seen from NC, equal to the Yukon deposit I feel was from the talc mine at Staley, Randolph Co., NC. I visited with Boyd Mattison in Yancey Co., NC many years ago and he showed to me a flat of killer deep blue gemmy lazulite crystals that were on xllized pyrophyllite and quartz from there that he had collected in the 60's. Some were stacked upon each other like Spanish pyrites in habit and stuck out of matrix! I tried my best to trade or buy one but he wouldn't part with a single one. I'd love to know where these fine specimens ended up. I collected at Staley some years back and did find one loose gemmy partial xl that I found sifting loose mine material but only one without matrix. Like Laurie was saying, there are a number of Lazulite localities in NC and the one that I've read about but never seen is Coffee Gap, Stokes Co., NC. Clubb (Chubb) Mnt., Gaston Co. is probally the most prolific source that I know for collectors.
  
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Re: Lazulite - January 2015
Reply #6 - Jan 14th, 2015 at 2:38pm
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The 1987 Virginia Mineral Locality Index lists lazulite as present at the Willis Mountain Kyanite Mine.  Willis Mountain is predominantly a kyanite quartzite. (Was kyanite quartzite also the mined rock at Graves Mountain?)  I have yet to go on a Willis Mountain field trip; Virginia clubs occassionally sponsor trips, but I think they are just for looking around, not collecting.  Geology maps show the kyanite quartzite in various places nearby, so that part of central Virginia is on my "someday" list of exploring.
  
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Re: Lazulite - January 2015
Reply #7 - Jan 14th, 2015 at 3:45pm
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     Another VA reference to lazulite was in context of a 1986 Virginia Minerals newsletter (vol 32 no 1) about a rare mineral being found at Willis Mountain:  "The rare mineral trolleite, previously unreported from Virginia, has recently been discovered in Buckingham County. [...] Additional new minerals noted from the Willis Mountain site include apatite, native sulfur, crandallite-florencite and lazulite-scorzalite series minerals."
     Seeing that this is an internet discussion forum, would trolleite (pronounced troll-ee-ite) be an appropriate Mineral of the Month?  I'm thankful we have no trolls on the lounge who might claim this as their mineral namesake.
  
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Re: Lazulite - January 2015
Reply #8 - Jan 14th, 2015 at 10:13pm
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Lots of interesting local information, thank you all.
I would very much like to see some of the Randolph County lazulite.
Figures the gemmiest would be rumored from that county. Wink

All I have is the Graves Mtn material. Not complaining.
I have read that the Graves matrix is a white "sandstone".
I wonder what the VA quartzite matrix looks like and how it might compare?
Here's a piece from Graves with large, a few 1" across, lazulite crystals
collected by Chris Whitley.


  

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Laurie Adams
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Re: Lazulite - January 2015
Reply #9 - Jan 15th, 2015 at 7:29am
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Joe, there are varying degrees of metamorphism in the rocks at Graves, as exemplified in the quartzite there, which ranges from very hard almost vitreous quartzite to very crumbly "sandstone", that was not changed all that much due to heat and pressure and therefore retains much of the characteristics of the original sandstone.  This crumbly rock should at the least be called a meta-sandstone, but the majority of the Graves material would be a true quartzite.  Plus there are gradations between the two units.  Both units contain Lazulite.  Many diggers call the crumbly unit "sugar quartz" for obvious reasons.  Tim, Willis Mtn. has unfortunately been closed to clubs for several years.   Most of the kyanite there is grey and unattractive, but some zones do contain narrow blades with decent blue color.  The lazulite there only occurs in small trace amounts and specks to my knowledge.  The quartzite there is intermediate in hardness between the two extremes found at Graves.  Thanks Mike for mentioning the Coffee Gap reference.  I have wondered about this for decades and have spent a good bit of time investigating.  The same reference also mentions fluorite there.  I believe both of these to probably be erroneous.  These were very old identifications (1800's?) that were often wrong, no field evidence could be found, no anecdotal evidence could be found, and the local geology does not fit with the occurrence of these minerals.  So I consider this very suspect.  Anyone with any info on this is asked to please share it with us. 
  
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Re: Lazulite - January 2015
Reply #10 - Jan 15th, 2015 at 8:15am
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Joe,

You mentioned the Staley lazulite. There use to be (I assume still is) a road once gravel probally paved by now that folks where building nice homes off of that went right beside the tailing piles of the old talc mine at Staley. It was literally right up to the road back then. Just off the road were numerous posted signs. I actually found my small gemmy fragment along the road banks but did find a local that said it was OK to look around, later finding out that it wasn't and the correct landowner refused access so I gave up on that site. I have a few specimens that I purchased some years ago some with rutile and lazulite others with just lazulite in pyrophylitte from there if you want a piece. These however are not gemmy but are deep blue and somewhat irregular masses. Boyd was the only one that I know who had gem grade blue xls of lazulite from there and they were killer but like I say, he wouldn't part with a single one. They were perched up on pyrophyllite and quartz with individual ones to about 3/8" in size very sharply formed. The Staley mine needs to be re-investigated to see what if any the collecting status might be. It was a dangerous pit but there were dump piles everywhere. I've got one piece from there with a single sharp pyrite xl in it. I've read that many large quartz crystals also came from there. I bet you that there are still many lazulite specimens buried in the dump piles if one could just dig them.
  
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Re: Lazulite - January 2015
Reply #11 - Jan 15th, 2015 at 7:32pm
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Laurie, yes, the sandstone-quartzite comparison was exactly what I was wondering about.
That makes perfect sense. Thankyou for the reply.

And thanks for the additional info about the Staley, Rockytop.
We're going to have check on that one. Wink
  
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Re: Lazulite - January 2015
Reply #12 - Jan 16th, 2015 at 1:15pm
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I don't recall what I was doing on September 28, 2014, but some other commitment prevented me from going on this field trip sponsored by a number of Virginia clubs.  A description is on the Gem and Mineral Society of the Virginia Peninsula's site at:

http://gmsvp.weebly.com/uploads/3/1/2/7/3127689/2014-10_gmsvp_newsletter.pdf

Photos are from the newsletter.

I had thought look-see field trips were all that was going on at Willis Mountain, but apparently collecting is allowed on club sponsored trips.

GMSVP's announcement offered this description:  COLLECTING: Willis Mountain is what's known as a monadnock. The kyanite exposure resisted weathering and, as the surrounding area was eroded and weathered away, the mountain outcrop was left standing. This is very much like the famous Graves Mountain kyanite mine in Georgia. The center of the mountain has been mostly mined away. We should be able to find plenty of white kyanite blades in the massive kyanite quartzite; pyrite; quartz; hematite with some iridescent, red mica, apatite and possibly some blue kyanite and pale green trolleite. Some of the white kyanite here fluoresces a beautiful light blue as well as some of the quartz.

The kyanite and matrix photo from their newsletter is grainy but seems consistent with Laurie's description as being in between the Graves extremes.

Graves Mountain seems the better spot for sure.  But if these Virginia trips continue and circumstances allow, I will likely see the much-closer Willis Mountain first.  I think I have a better chance of finding more blue kyanite in Robert's creek next time I visit Raleigh! But seeing the Willis Mountain operations would be cool. 

Willis Mountain is a family-owned operation.  They chose the "environment" route after mining out Baker Mountain.

http://www.kyanite.com/environment.html

"The Baker Mountain mine was Kyanite Mining Corp.’s first mine and mineral processing plant. This facility was an active kyanite mine from the early 1920’s until the late 1970’s, when mining activities were discontinued. Baker Mountain has been transformed into a land reclamation showpiece."

"Kyanite Mining Corporation plans to restore the original plant structures and open the entire facility to the public as a mining museum and environmental education center."

That has been on their web site for a few years at least.  Have not heard anything new on their plans.  Even though it would have been nice to have preserved some collecting at Baker Mountain, the museum and education center should be good for rockhounding in central Virginia.  The region's economic development crowd can't seem to get their thinking much past light industrial parks and road building.  So I hope KMC is successful in their venture.
  

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Re: Lazulite - January 2015
Reply #13 - Jan 16th, 2015 at 8:57pm
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Hi,

Blue stuff on rocks - huh - seems like I should have found some of this Lazulite - maybe I will now that I know what I'm looking for...but per Tim's point about having better luck finding Kyanite in Mine Creek, here's some pieces

The larger one is about the size of a tennis ball and the two smaller ones are finger sized.

There seems to be brown, white and blue blades to be found - and a fair amount of it - once you know what to look for.

cheers,
r
  

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Re: Lazulite - January 2015
Reply #14 - Jan 19th, 2015 at 9:36pm
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Was looking to see what I could find on the old Staley mine
and lo and behold lookee here,
(hope the link works),
http://www.johnbetts-fineminerals.com/jhbnyc/mineralmuseum/picshow.php?id=31437
  
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