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Contents

   



(Top)
 


1 Name  





2 Use  





3 Formation  





4 Occurrence  



4.1  Roseland-Piney River district, Virginia  







5 References  














Nelsonite







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From Wikipedia, the free encyclopedia
 


Nelsonite
Igneous rock
A speckled rock with black (ilmenite) and white (apatite) grains
Nelsonite from Nelson County, Virginia
Composition
Ilmenite and apatite
Identification[1]
Formula FeO.TiO2.nFe2O3

Ca3(F,Cl)(PO4)3

Hardness 5 - 6
Specific gravity 3.7 - 4.1 bulk; ilmenite: 4.5-5.0
Streak ilmenite: black to brownish-red

apatite: white

Color black metallic and light-colored
Habit even-granular texture
Luster metallic to sub-metallic
Fracture conchoidal
Tenacity brittle
Texture holocrystalline

Nelsonite is an igneous rock primarily constituted of ilmenite and apatite, with anatase, chlorite, phosphosiderite, talc and/or wavellite appearing as minor components. Rocks are equigranular with a grain size around 2 – 3 mm.[2] The black ilmenite is slightly magnetic while the whitish apatite is not.[3]

Name

[edit]

It was named for Nelson County, Virginia, and is also found in that state's Amherst and Roanoke counties. In 2016, the Virginia legislature designated it as the official State RockofVirginia.[4]

Use

[edit]

At one time, it was mined for the primary extraction of titanium dioxide. Titanium dioxide from ilmenite is used as a white paint pigments[5] and in the early 1900's as a colorant of artificial teeth.[1][6] The calcium phosphate from apatite is used as agricultural fertilizer.[6] While no active mining of Nelsonite occurs in Virginia, active mining occurs in parts of China for rare-earth elements.[3][6][2]

Formation

[edit]

Anorthosite-related nelsonite occurs mainly as veins and lensoidal intrusions in anorthosite complex or wall rocks.[7] The Fe–Ti–P-rich magma liquids formed immiscible and eutectic mixtures crystallizing around 850-1,000 °C followed by intense fractionation.[8][6] Disagreement exists on the role liquid immiscibility plays in generating nelsonite and Fe–Ti oxides ore.[7] It is not common to have such relatively large density differentials of mineral constituents as seen in Nelsonite; ilmenite (4.7–5.2 g/cm3) and apatite (~ 3.5 g/cm3).[7] Nelsonites experience differential weathering. Exposed apatite within the Nelsonite is readily removed through solution by meteoric waters that can result in a cellular or sponge-like ilmenite mass.[1]

Occurrence

[edit]

Nelsonites are generally associated with anorthosite intrusions and scarce worldwide. [7] Nelsonite occurs at various localities, not limited to: Nelson, Amherst, & Roanoke Counties, Va.; Carthage & Cheney Pond, N.Y.; Laramie, W.Va.; Washington State; Quebec, Canada; and China.[3]

Roseland-Piney River district, Virginia

[edit]

The nelsonite occurs in alkalic Roseland anorthosite, and in gneiss, granulite, and charnockitic rocks surrounding the anorthosite. Multiple varieties of equigranular nelsonite are present in the Roseland-Piney River district.[1]

The prefixes ilmenite, rutile, magnetite, biotite, and hornblende denote special richness of the rocks in these minerals.[1]

References

[edit]
  1. ^ a b c d e Watson, Thomas; Taber, Stephen (1913). Bulletin 003-A, Geology of the Titanium and Apatite Deposits of Virginia (Report). Virginia Geological Survey. Retrieved 2022-04-22.
  • ^ a b Kolker, Allan (1982). "Mineralogy and Geochemistry of Fe-Ti Oxide and Apatite (Nelsonite) Deposits and Evaluation of the Liquid Immiscibility Hypothesis". Economic Geology. 77 (5): 1146–1158. CiteSeerX 10.1.1.918.2121. doi:10.2113/gsecongeo.77.5.1146.
  • ^ a b c "Nelsonite State Rock Initiative". Piedmont Virginia Community College. Retrieved 2016-09-14.
  • ^ "SB 352 Nelsonite; designating as state rock, etc". State of Virginia. Retrieved 2016-05-11.
  • ^ Johnson, Stanley (August 1964). Iron and Titanium Mineral Pigments in Virginia (PDF) (Report). Virginia Division of Mineral Resources. Retrieved 2022-04-22.
  • ^ a b c d "Virginia's State Rock: Nelsonite". William & Mary University. Retrieved 2022-04-20.
  • ^ a b c d "Origin of nelsonite and Fe–Ti oxides ore of the Damiao anorthosite complex, NE China: Evidence from trace element geochemistry of apatite, plagioclase, magnetite and ilmenite". Ore Geology Reviews. Retrieved 2022-04-18.
  • ^ Herz, Norman; Force, Eric (1987). "Geology and Mineral Deposits of the Roseland District of Central Virginia" (PDF). USGS. 1371: 4. doi:10.3133/pp1371.

  • Retrieved from "https://en.wikipedia.org/w/index.php?title=Nelsonite&oldid=1218942017"

    Categories: 
    Igneous rocks
    Symbols of Virginia
    Nelson County, Virginia
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