SUPPORT US. If mindat.org is important to you, click here to donate to our Fall 2019 fundraiser!
Log InRegister
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 ElementsBooks & Magazines
Minerals by PropertiesMinerals by ChemistryAdvanced Locality SearchRandom MineralRandom LocalitySearch by minIDLocalities Near MeSearch ArticlesSearch GlossaryMore Search Options
Search For:
Mineral Name:
Locality Name:
Keyword(s):
 
The Mindat ManualAdd a New PhotoRate PhotosLocality Edit ReportCoordinate Completion ReportAdd Glossary Item
Mining CompaniesStatisticsUsersMineral MuseumsMineral Shows & EventsThe Mindat DirectoryDevice Settings
Photo SearchPhoto GalleriesNew Photos TodayNew Photos YesterdayMembers' Photo GalleriesPast Photo of the Day GalleryMineral Photography

Identity HelpRe:Garnet

1st Jan 2006 19:42 UTCIlkka Mikkola Expert

What species?

Small dark-brown anhedral crystals from the same cavity as the Mn-rich "apatite".

Apatite is dark greenish-brown.

Microprobeanalysis of the garnet:

SiO2 39.10 Al2O3 21.00 FeO 6.95 MnO2 11.20 MgO 7.90 CaO 12.10 Tot 98.25(w%)

Formula CaO 0.99 MgO 0.90 MnO 0:72 FeO 0.44 SiO2 2.98 Al2O3 1.91

I think that this is unusual analysis for a pegmatite garnet.

The pegmatite contains lot of usual red-brown spessartine,brown tourmaline,"columbite",vivianite,albite,quarz,muscovite, beusite,beryl and some

other normal pegmatite minerals.

Regards:Ilkka

1st Jan 2006 22:09 UTCAlan Plante

Wouldn't that make it a grossular composition with an anomolously high Mg content? I don't think there are solid solution series between grossular and any of the Mg species - pyrope, majorite and knorringite. I think the series that grossular form are grossular-andradite (Al-Fe substitution), grossular-uvarovite (Al-Cr substitution), and the two nominal "hydrogarnets", katoite and hibschite (Si-OH substitution???). Dana 8th does note, though, regarding grossular: "However, solid solution to varying extent occurs with other garnets." So perhaps it is not all that anomolous? (Don't you just love it when authors make vague statements like that, not presenting any data to support them??? :~} )


Regards


Alan

3rd Jan 2006 06:58 UTCIlkka Mikkola Expert

Hello Alan

Thank you.


Best regards.



Ilkka
 
Mineral and/or Locality  
Mindat.org is an outreach project of the Hudson Institute of Mineralogy, a 501(c)(3) not-for-profit organization. Public Relations by Blytheweigh.
Copyright © mindat.org and the Hudson Institute of Mineralogy 1993-2019, except where stated. Most political location boundaries are © OpenStreetMap contributors. Mindat.org relies on the contributions of thousands of members and supporters.
Privacy Policy - Terms & Conditions - Contact Us Current server date and time: December 10, 2019 07:55:00
Go to top of page