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!
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Biotite from
Magnet Cove, Hot Spring County, Arkansas, USA


04722390017272013621862.jpg
Phlogopite

Jones Mill Quarry, Magnet Cove, Hot Spring County, Arkansas, USA
09606450017272012553684.jpg
Phlogopite, etc.

Jones Mill Quarry, Magnet Cove, Hot Spring County, Arkansas, USA
04776760017272011532603.jpg
Biotite

Cove Creek Bridge and The Branch area, Magnet Cove, Hot Spring County, Arkansas, USA
04934780017272012573644.jpg
Phlogopite, etc.

Jones Mill Quarry, Magnet Cove, Hot Spring County, Arkansas, USA
01055410017368952454656.jpg
Phlogopite

Jones Mill Quarry, Magnet Cove, Hot Spring County, Arkansas, USA
04177860017368952456395.jpg
Phlogopite, etc.

Jones Mill Quarry, Magnet Cove, Hot Spring County, Arkansas, USA
09545510017730985639159.jpg
Biotite

Cove Creek Bridge and The Branch area, Magnet Cove, Hot Spring County, Arkansas, USA
09024780017368952451161.jpg
Phlogopite, etc.

Jones Mill Quarry, Magnet Cove, Hot Spring County, Arkansas, USA
04722390017272013621862.jpg
Phlogopite

Jones Mill Quarry, Magnet Cove, Hot Spring County, Arkansas, USA
09606450017272012553684.jpg
Phlogopite, etc.

Jones Mill Quarry, Magnet Cove, Hot Spring County, Arkansas, USA
04776760017272011532603.jpg
Biotite

Cove Creek Bridge and The Branch area, Magnet Cove, Hot Spring County, Arkansas, USA
04934780017272012573644.jpg
Phlogopite, etc.

Jones Mill Quarry, Magnet Cove, Hot Spring County, Arkansas, USA
Locality type:Census-designated Place
Classification
Species:'Biotite' (not an IMA approved species)
Formula:K(Fe2+/Mg)2(Al/Fe3+/Mg/Ti)([Si/Al/Fe]2Si2O10)(OH/F)2
Age information
Maximum recorded age:102 ± 8 Ma
Minimum recorded age:94.2 ± 0.2 Ma
Sample ages:
Recorded ageGeologic TimeSampleDating method
197 ± 5 MaLate/Upper Cretaceous - K-Ar
2100 ± 5 MaLate/Upper Cretaceous - K-Ar
3102 ± 8 MaEarly/Lower Cretaceous - Rb-Sr
4102 ± 8 MaEarly/Lower Cretaceous - Rb-Sr
594.4 ± 0.2 MaLate/Upper Cretaceous - Ar-Ar
694.2 ± 0.2 MaLate/Upper Cretaceous - Ar-Ar
Sample references:
1 -
Zartman, R.E., Brock, M.R., Heyl, A.V., and Thomas, H.H. (1967) K-Ar and Rb-Sr ages of some alkalic intrusive rocks from central and eastern United States. American Journal of Science, vol. 265, pp. 848-870.
2 -
Zartman, R.E., Brock, M.R., Heyl, A.V., and Thomas, H.H. (1967) K-Ar and Rb-Sr ages of some alkalic intrusive rocks from central and eastern United States. American Journal of Science, vol. 265, pp. 848-870.
3 -
Zartman, R.E., Brock, M.R., Heyl, A.V., and Thomas, H.H. (1967) K-Ar and Rb-Sr ages of some alkalic intrusive rocks from central and eastern United States. American Journal of Science, vol. 265, pp. 848-870.
4 -
Zartman, R.E., Brock, M.R., Heyl, A.V., and Thomas, H.H. (1967) K-Ar and Rb-Sr ages of some alkalic intrusive rocks from central and eastern United States. American Journal of Science, vol. 265, pp. 848-870.
5 -
Baksi, A.K. (1997) The Timing of Late Cretaceous Alkalic Igneous Activity in the Northern Gulf of Mexico Basin, Southeastern USA. The Journal of Geology, Vol. 105, No. 5, pp. 629-643.
6 -
Baksi, A.K. (1997) The Timing of Late Cretaceous Alkalic Igneous Activity in the Northern Gulf of Mexico Basin, Southeastern USA. The Journal of Geology, Vol. 105, No. 5, pp. 629-643.
Confirmation
Validity:Believed Valid
Associated Minerals Based on Photo Data:
Carbonatite1
Brookite1
Data
Mineral Data:Click here to view Biotite data
Locality Data:Click here to view Magnet Cove, Hot Spring County, Arkansas, USA
Data Identifiers
Mindat Occurrence Record ID:652154
Long-form Identifier:1:3:652154:7
GUID (UUID V4):0
Localities for Biotite in this Region
Cove Creek Bridge and The Branch area, Magnet Cove, Hot Spring County, Arkansas, USA
Diamond Jo Quarry, Magnet Cove, Hot Spring County, Arkansas, USA
Jones Mill Quarry, Magnet Cove, Hot Spring County, Arkansas, USA
Kimzey Calcite Quarry (Calcite Hill), Magnet Cove, Hot Spring County, Arkansas, USA
Kimzey Magnetite Mine, Magnet Cove, Hot Spring County, Arkansas, USA
Magnet Cove Baptist Church area, Magnet Cove, Hot Spring County, Arkansas, USA
Magnet Cove Rutile Company deposits, Magnet Cove, Hot Spring County, Arkansas, USA
Perovskite Hill, Magnet Cove, Hot Spring County, Arkansas, USA
References
Erickson, Ralph Leroy
Blade, Lawrence Vernon (1963) Geochemistry and petrology of the alkalic igneous complex at Magnet Cove, Arkansas. USGS Prof. Paper 425.
Shockley, Woodland G. (1976) Mineral Collecting in Magnet Cove, Arkansas. Rocks & Minerals, 51 (10) 495-507 doi:10.1080/00357529.1976.11762161
Eby, Nelson; Charnley, Norman; Tiella, Gino; Burkhardt, Louis (2025) The Arkansas Alkaline Province, Southeastern USA: A Synthesis of New and Existing Chemical and Petrologic Data and Petrogenetic Considerations. Minerals, 15 (11). doi:10.3390/min15111133
 
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