Vote for your favorite mineral in #MinCup26! - Sphalerite vs. Anorthite
Both zinc ore Sphalerite and calcium plagioclase feldspar Anorthite have perfect cleavage that will split cleanly if you hit them with a hammer, but only one can claim a larger split of your votes!
Log InRegister
Quick Links : The Mindat ManualThe Rock H. Currier Digital LibraryMindat Newsletter [Free Download]
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 TimeExplore Fossils
Minerals by PropertiesMinerals by ChemistryMineral Visual ExplorerAdvanced 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 MuseumsClubs & OrganizationsMineral Shows & EventsThe Mindat DirectoryDevice SettingsThe Mineral QuizTime Machine
Photo SearchPhoto GalleriesSearch by ColorPhoto Colour ExplorerNew Photos TodayNew Photos YesterdayMembers' Photo GalleriesPast Photo of the Day GalleryPhotography

Illite from
Thornthwaite Mine, Thornthwaite, Above Derwent, Allerdale, Cumbria, England, UK


Locality type:Mine
Classification
Species:Muscovite var: Illite
Formula:K0.65Al2.0[Al0.65Si3.35O10](OH)2
Age information
Maximum recorded age:365 Ma
Minimum recorded age:311 Ma
Sample ages:
Recorded ageGeologic TimeSampleDating method
1311 MaPennsylvanian - K-Ar
2362 MaLate/Upper Devonian - K-Ar
3339 MaMississippian - K-Ar
4314 MaPennsylvanian - K-Ar
5365 MaLate/Upper Devonian - K-Ar
Sample references:
1 -
Ineson, P. R., Mitchell, J. G. (1974) K-Ar isotopic age determinations from some Lake District mineral localities. Geological Magazine, 111 (6). 521-537 doi:10.1017/s0016756800041571
2 -
Ineson, P. R., Mitchell, J. G. (1974) K-Ar isotopic age determinations from some Lake District mineral localities. Geological Magazine, 111 (6). 521-537 doi:10.1017/s0016756800041571
3 -
Ineson, P. R., Mitchell, J. G. (1974) K-Ar isotopic age determinations from some Lake District mineral localities. Geological Magazine, 111 (6). 521-537 doi:10.1017/s0016756800041571
4 -
Ineson, P. R., Mitchell, J. G. (1974) K-Ar isotopic age determinations from some Lake District mineral localities. Geological Magazine, 111 (6). 521-537 doi:10.1017/s0016756800041571
5 -
Ineson, P. R., Mitchell, J. G. (1974) K-Ar isotopic age determinations from some Lake District mineral localities. Geological Magazine, 111 (6). 521-537 doi:10.1017/s0016756800041571
Confirmation
Validity:Believed Valid
Data
Mineral Data:Click here to view Illite data
Locality Data:Click here to view Thornthwaite Mine, Thornthwaite, Above Derwent, Allerdale, Cumbria, England, UK
Data Identifiers
Mindat Occurrence Record ID:16541
Long-form Identifier:1:3:16541:3
GUID (UUID V4):0
Nearest other occurrences of Illite
4.8km (3.0 miles) ⓘForce Crag Mine, Coledale, Above Derwent, Allerdale, Cumbria, England, UK
6.8km (4.2 miles) ⓘYewthwaite Mine, Newlands Valley, Above Derwent, Allerdale, Cumbria, England, UK
7.3km (4.5 miles) ⓘBrundholme Mine (Glenderaterra Mine; Blencathra Mine), Glenderaterra Valley, Threlkeld, Eden, Cumbria, England, UK
7.3km (4.5 miles) ⓘGoldscope Mine, Newlands Valley, Above Derwent, Allerdale, Cumbria, England, UK
8.8km (5.5 miles) ⓘCastle Nook Mine, Newlands Valley, Above Derwent, Allerdale, Cumbria, England, UK
10.1km (6.3 miles) ⓘThrelkeld Mine, Threlkeld, Threlkeld, Eden, Cumbria, England, UK
11.6km (7.2 miles) ⓘRoughton Gill, Caldbeck, Allerdale, Cumbria, England, UK
11.6km (7.2 miles) ⓘRoughton Gill Mine, Roughton Gill, Caldbeck, Allerdale, Cumbria, England, UK
12.2km (7.6 miles) ⓘCarrock Mine, Mungrisdale, Eden, Cumbria, England, UK
13.4km (8.3 miles) ⓘWad Mine, Seathwaite, Borrowdale, Allerdale, Cumbria, England, UK
References
Day, Harry (1999) BMS Database, British Micromount Society.
 
and/or  
Mindat.org® is an outreach project of the Hudson Institute of Mineralogy, a 501(c)(3) not-for-profit organization. Mindat® and mindat.org® are registered trademarks of the Hudson Institute of Mineralogy.
Copyright © mindat.org and the Hudson Institute of Mineralogy 1993-2026, 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 and Ida Chau.
Content on this site may not be used to train, fine-tune, or otherwise develop artificial intelligence or machine learning models without prior written permission - see our Terms & Conditions.
To cite: Ralph, J., Von Bargen, D., Martynov, P., Zhang, J., Que, X., Prabhu, A., Morrison, S. M., Li, W., Chen, W., & Ma, X. (2025). Mindat.org: The open access mineralogy database to accelerate data-intensive geoscience research. American Mineralogist, 110(6), 833–844. doi:10.2138/am-2024-9486.
Privacy Policy - Terms & Conditions - Contact Us / DMCA issues - Report a bug/vulnerability Current server date and time: September 3, 2026 06:45:01
Go to top of page