Home PageAbout MindatThe Mindat ManualHistory of MindatCopyright StatusWho We AreContact UsAdvertise on Mindat
Donate to MindatCorporate SponsorshipSponsor a PageSponsored PagesMindat AdvertisersAdvertise on Mindat
Learning CenterWhat is a mineral?The most common minerals on earthInformation for EducatorsMindat ArticlesThe ElementsThe Rock H. Currier Digital LibraryGeologic Time
Minerals by PropertiesMinerals by ChemistryAdvanced Locality SearchRandom MineralRandom LocalitySearch by minIDLocalities Near MeSearch ArticlesSearch GlossaryMore Search Options
The Mindat ManualAdd a New PhotoRate PhotosLocality Edit ReportCoordinate Completion ReportAdd Glossary Item
Mining CompaniesStatisticsUsersMineral MuseumsClubs & OrganizationsMineral Shows & EventsThe Mindat DirectoryDevice SettingsThe Mineral Quiz
Photo SearchPhoto GalleriesSearch by ColorNew Photos TodayNew Photos YesterdayMembers' Photo GalleriesPast Photo of the Day GalleryPhotography
╳Discussions
💬 Home🔎 Search📅 LatestGroups
EducationOpen discussion area.Fakes & FraudsOpen discussion area.Field CollectingOpen discussion area.FossilsOpen discussion area.Gems and GemologyOpen discussion area.GeneralOpen discussion area.How to ContributeOpen discussion area.Identity HelpOpen discussion area.Improving Mindat.orgOpen discussion area.LocalitiesOpen discussion area.Lost and Stolen SpecimensOpen discussion area.MarketplaceOpen discussion area.MeteoritesOpen discussion area.Mindat ProductsOpen discussion area.Mineral ExchangesOpen discussion area.Mineral PhotographyOpen discussion area.Mineral ShowsOpen discussion area.Mineralogical ClassificationOpen discussion area.Mineralogy CourseOpen discussion area.MineralsOpen discussion area.Minerals and MuseumsOpen discussion area.PhotosOpen discussion area.Techniques for CollectorsOpen discussion area.The Rock H. Currier Digital LibraryOpen discussion area.UV MineralsOpen discussion area.Recent Images in Discussions
Identity HelpAssuming this is Prehnite
20th Apr 2017 21:41 UTCStephen C. Blyskal Expert
20th Apr 2017 22:18 UTCKevin Conroy Manager
Is there any matrix or staining on the back of the specimen?
Cheers,
Kevin
20th Apr 2017 23:48 UTCHarold Moritz 🌟 Expert
21st Apr 2017 03:38 UTCStephen C. Blyskal Expert
Not a scrap of matrix anywhere on it. Nothing in the crystal form or color really screams "locality" to me.
21st Apr 2017 03:40 UTCStephen C. Blyskal Expert
I'll check it out, but I am not hopeful. I have a good selection from that quarry and all the larger specimens are epimorphs. This is 10 cm of solid crystal.
21st Apr 2017 03:49 UTCAlfredo Petrov Manager
21st Apr 2017 04:51 UTCKevin Conroy Manager
21st Apr 2017 06:35 UTCKeith Compton 🌟 Manager
Sure looks a lot like Prehnite.
My guess, and it is only a guess, is that it looks a lot like material from Merelani, Tanzania.
The Tanzanian material is relatively new on the market (at least in quantity). If someone had an unlabelled piece similar to that they could easily have simply guessed New Jersey as the source.
Cheers
Keith
21st Apr 2017 18:52 UTCPeter Andresen Expert
I think you will have to put locality unknown on this one.
22nd Apr 2017 16:30 UTCDonald B Peck Expert
25th Apr 2017 21:51 UTCStephen C. Blyskal Expert
I held this under a daylight balanced fluorescent light and it turns this color. Under a bright white LED light it turns an off-white!
I have a hardness kit with metal rods with definite tip hardness. Hate to do destructive testing. I saw scratches with the 5, 6 and 7 but not with the 4.
So if the hardness is between 4 - 5 it is probably not prehnite.
I am going to the Fine Mineral Show - Woodlands this weekend and will take this specimen with me, since I want to get a base made. There are 25+ mineral dealers there. Maybe one of them will recognize it.
25th Apr 2017 23:15 UTCPeter Chin Expert
26th Apr 2017 15:51 UTCMarco Pellecchia
No assuming this is prehnite, It looks like stilbite to me. In particular, stilbite forming globular clusters, as in the so called "puflerite".
Please, take a look here (colour is different):
https://www.mindat.org/photo-273487.html
https://www.mindat.org/photo-220261.html
Regards
Marco
26th Apr 2017 17:52 UTCJeff Weissman Expert
26th Apr 2017 19:51 UTCStephen C. Blyskal Expert
You may have something there. The exterior form is very similar, particularly with the specimen from Poland. I will have to check this out. The color is the problem, particularly the color change based on what kind of light it is under. I tried my hardness 6 pick on one of my Paterson/Prospect Park prehnite specimens for comparison and it did not scratch it, so I am more convinced that I don't really have prehnite, but some other silicate mineral.
26th Apr 2017 20:05 UTCStephen C. Blyskal Expert
-------------------------------------------------------
> Here is a prehnite from Paterson, I have no reason
> to doubt either the ID or the locality - child
> photos have prior labels and other views. The
> morphology is similar to what Stephen has posted,
> both having flat curved surfaces
>
>
Jeff,
I have a few specimens from the Paterson area that show similar crystal form, but they don't look anything like the specimen above. The 10cm long dimension is the real problem, since prehnite tends to form 2mm to 2.5 cm crusts on other earlier minerals in most localities. It just does not mound up like this specimen displays. More and more convinced it is not prehnite at all. May send a sample to Excalibur Minerals for testing.
26th Apr 2017 21:11 UTCKevin Conroy Manager
27th Apr 2017 02:06 UTCKeith Compton 🌟 Manager
Don't forget - Prehnite has a hardness of 6-6.5 so a 6 pick might not scratch it.
Cheers
Keith
6th Jan 2018 05:11 UTCStephen C. Blyskal Expert
My plan for 2018 is to harvest a small fragment from the bottom of the specimen and send it off for analysis. Any recommendations on where to send it other than Excalibur?
6th Jan 2018 08:25 UTCAlfredo Petrov Manager
For silicates composed mainly of light weight elements like Al, Ca, Na, K, etc, XRD is likely to give you a more useful result than EDS.
6th Jan 2018 17:12 UTCDonald B Peck Expert
7th Jan 2018 00:28 UTCRuss Rizzo Expert
10th Jan 2018 22:10 UTCStephen C. Blyskal Expert
10th Jan 2018 23:10 UTCIan Nicastro
17th Jan 2018 18:06 UTCStephen C. Blyskal Expert
According to Wendel Minerals, the dealer I got this from, this specimen came out of an old collection. I have seen the new Brucite at the last Tucson show and those high end specimens have a color very different from my specimen. Thanks for bringing up the idea though. We'll see once I get results back from Attard Minerals.
17th Jan 2018 18:11 UTCStephen C. Blyskal Expert
Here are three additional photos taken with the intent to show the structure on the underside of the specimen. I specifically used shadow to illustrate the rods that make up each of the "scoops" that pile up on each other.
17th Jan 2018 18:56 UTCAlan Pribula
17th Jan 2018 19:43 UTCNik Nikiforou
This prehnite is definitely from the Lower New St. Quarry in Paterson, NJ.
I've handled about a dozen pieces of this material which came from a small find in the summer of 2011.
I hope this solves your mystery, although the material that I've seen was definitely not from an old collection.
Best,
Nik Nikiforou
18th Jan 2018 23:19 UTCStephen C. Blyskal Expert
I have several pieces from this find and know the "midnight miners" who opened the pocket. Comparing those specimens to the above unknown shows several differences. For one, my specimen is not 6 - 6.5 in hardness (tested with hardness picks) and two, it is fluorescent under SW, MW and LW on my Way Too Cool light. A visual comparison shows the ridges of crystal terminations on your specimen (and all the ones I've seen from this find) and my specimen shows curved surfaces that are subparallel.
I did some extensive checking of the brucite photo archive over the last two days and have concluded that despite some similarities this mineral is unlikely to be my "Mineral X".
19th Jan 2018 01:26 UTCNik Nikiforou
Thanks for the correction. My specimens are not fluorescent.
Be well,
Nik
Mindat.org is an outreach project of the Hudson Institute of Mineralogy, a 501(c)(3) not-for-profit organization.
Copyright © mindat.org and the Hudson Institute of Mineralogy 1993-2024, except where stated. Most political location boundaries are © OpenStreetMap contributors. Mindat.org relies on the contributions of thousands of members and supporters. Founded in 2000 by Jolyon Ralph.
Privacy Policy - Terms & Conditions - Contact Us / DMCA issues - Report a bug/vulnerability Current server date and time: April 23, 2024 06:30:44
Copyright © mindat.org and the Hudson Institute of Mineralogy 1993-2024, except where stated. Most political location boundaries are © OpenStreetMap contributors. Mindat.org relies on the contributions of thousands of members and supporters. Founded in 2000 by Jolyon Ralph.
Privacy Policy - Terms & Conditions - Contact Us / DMCA issues - Report a bug/vulnerability Current server date and time: April 23, 2024 06:30:44