Nelsonite is an igneous rock primarily constituted of

ilmenite Ilmenite is a titanium-iron oxide mineral with the idealized formula . It is a weakly magnetic black or steel-gray solid. Ilmenite is the most important ore of titanium and the main source of titanium dioxide, which is used in paints, printing ...

and apatite, with

anatase Anatase is a metastable mineral form of titanium dioxide (TiO2) with a tetragonal crystal structure. Although colorless or white when pure, anatase in nature is usually a black solid due to impurities. Three other polymorphs (or mineral form ...

, chlorite,

phosphosiderite Phosphosiderite is a rare mineral named for its main components, phosphate and iron. The siderite at the end of phosphosiderite comes from the word "sideros", the Greek word for iron. It was published in 1890, and has been a valid species since p ...

talc Talc, or talcum, is a clay mineral, composed of hydrated magnesium silicate with the chemical formula Mg3Si4O10(OH)2. Talc in powdered form, often combined with corn starch, is used as baby powder. This mineral is used as a thickening agent a ...

and/or

wavellite Wavellite is an aluminium basic phosphate mineral with formula Al3( P O4)2(O H, F)3·5 H2O. Distinct crystals are rare, and it normally occurs as translucent green radial or spherical clusters. Discovery and occurrence Wavellite was first d ...

appearing as minor components. Rocks are equigranular with a grain size around 2 - 3 mm. The black ilmenite is slightly magnetic while the whitish apatite is not.

Name

It was named for

Nelson County, Virginia Nelson County is a county located in the Commonwealth of Virginia, in the United States. As of the 2020 census, the population was 14,775. Its county seat is Lovingston. Nelson County is part of the Charlottesville, VA Metropolitan Statistic ...

, and is also found in that state's Amherst and Roanoke counties. In 2016, the Virginia legislature designated it as the official

State Rock Leaders of states in the U.S. which have significant mineral deposits often create a state mineral, rock, stone or gemstone to promote interest in their natural resources, history, tourism, etc. Not every state has an official state mineral, rock, ...

Virginia Virginia, officially the Commonwealth of Virginia, is a state in the Mid-Atlantic and Southeastern regions of the United States, between the Atlantic Coast and the Appalachian Mountains. The geography and climate of the Commonwealth ar ...

Use

At one time, it was mined for the primary extraction of

titanium dioxide Titanium dioxide, also known as titanium(IV) oxide or titania , is the inorganic compound with the chemical formula . When used as a pigment, it is called titanium white, Pigment White 6 (PW6), or CI 77891. It is a white solid that is insolub ...

. Titanium dioxide from ilmenite is used as a white paint pigments and in the early 1900's as a colorant of artificial teeth. The calcium phosphate from apatite is used as agricultural fertilizer. While no active mining of Nelsonite occurs in Virginia, active mining occurs in parts of China for

rare-earth element The rare-earth elements (REE), also called the rare-earth metals or (in context) rare-earth oxides or sometimes the lanthanides ( yttrium and scandium are usually included as rare earths), are a set of 17 nearly-indistinguishable lustrous silv ...

Formation

Anorthosite-related nelsonite occurs mainly as veins and lensoidal intrusions in anorthosite complex or wall rocks. The Fe–Ti–P-rich magma liquids formed immiscible and eutectic mixtures crystallizing around 850-1,000 °C followed by intense fractionation. Disagreement exists on the role liquid immiscibility plays in generating nelsonite and Fe–Ti oxides ore. 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). 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.

Occurrence

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

Roseland-Piney River district, Virginia

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. * Ilmenite nelsonite: the most abundant variety, commonly occurs in marginal parts of the anorthosite and in surrounding rocks near the anorthosite contact. * rutile nelsonite: occurs only within the anorthosite. * magnetite and biotite nelsonite: limited to the rocks surrounding the Roseland anorthosite. * hornblende nelsonite * gabbro-nelsonite: a rock intermediate in composition between gabbro and nelsonite The prefixes ilmenite, rutile, magnetite, biotite, and hornblende denote special richness of the rocks in these minerals.

References

{{reflist Igneous rocks Symbols of Virginia Nelson County, Virginia