Culpeper Rock Identified- as Diabase basalt

[GunnarMN]

The Culpeper Basin is a structural trough filled with sedimentary, metamorphic, and igneous rocks of Mesozoic age that border the eastern front of the Blue Ridge in northern Virginia. The basin extends 1,062 square miles from the Rapidan River near Madison Mills, Virginia, northeastward across the Potomac River and terminates just west of Frederick, Maryland.
The rock and mineral resources of the Culpeper basin are presently used for construction material, highway fill and building stone. The principal quarries, pits, mines, and prospects are shown on Map 4.11. Diabase is quarried for crushed aggregate and dimension stone, basalt is quarried for aggregate and crushed stone, and shale is extracted as a source of clay for brick manufacture. Future construction may require adequate quantities of crushed stone, brick clay, and aggregate at or near the surface and close to the area of use. Large reserves of some industrial materials are present, but new pits or quarries may be needed to fulfill the requirements economically before future construction commences. Inactive mineral producers include granite quarries, limestone quarries, and gneiss quarries.====AS YOU CAN SEE THE ROCK IS FULL OF IRON BETWEEN 12 AND 14%, DURING THE CREATACIOUSE WEATHERING THE ROCK WAS WEATHERED TO KAOLIN CLAY ENCREASING THE AMOUNT OF IRON POSSIBLY HIGHER THAT 14% THAT IS WHY THE SOIL IS RED AND HARD FOR DETECTORS TO GET THRU

 

[matthias]

WOW! Nice job Gunnar! HH. Matt

 

[JimmyCT]

Nice work detective! Wow, that must be a nightmare to hunt in.

 

[GunnarMN]

I think the ultimate badd ground would be up in the Iron range in minnesota.

 

[ryanchappell]

I think the ultimate badd ground would be up in the Iron range in minnesota.

Tell me what you think about this report. This is what we have in Birmingham, and Chattanooga and it probably runs to PA along the Appalachians. In Bham, locally to the north we have red iron ore, and to the south "brown" iron ore. I just learned reading this today that the red ore has more CaO, as apposed to quartz sand.

If I run a rare earth magnet through the black soil I find black pebble sized sandstone-like fragments stick to it. I am only detecting dimes at 1-5 inches deep with an E-Trac. If I unknowingly unearth a dime and accidently cover it with 2 inches of soil outside the hole I frequently can't see it scanning with the E-Trac.

http://pubs.usgs.gov/bul/0380e/report.pdf

 

[GunnarMN]

That is really intresting most of the ore has a Iron content of 30 to 40% that is high i think a PI machine would be in line , wish i could get some and do some tests I know the stuff up in minnesota has 60% to 70% iron in it the low grad stuff 40- 50 % I know I will eventully get a PI machine somday thanks for the cool link

 

[woodchiphustler]

That area was used to develope and test the TDI. The pulse must have a ground balance. How do I know????????????????? Top secret, research TDI field manual, relic, see if you can id the name.

 

[ryanchappell]

That is really intresting most of the ore has a Iron content of 30 to 40% that is high i think a PI machine would be in line , wish i could get some and do some tests I know the stuff up in minnesota has 60% to 70% iron in it the low grad stuff 40- 50 % I know I will eventully get a PI machine somday thanks for the cool link

Yeah, but I can't metal detect neighborhoods looking for silver coins with PI.


I was reading about the CTX3030 today and found out that the high mineralization Ground Coin Seperation mode (which did not pass the Cullpepper test) is not optimal for trash/junk seperation, and the High trash is not optimal for high mineralization. Basically FBS is a branch of technology geared for trash seperation, not compatable with minerals... CTX in Devil Soil.

The significant deposits that they wrote about are 40%, but you probably have seen those black veins of iron rock that are a few feet wide in stream beds like I have seen. Those are probably the 70%+ rocks? There just is not enough to round up meaningful amounts for industry.

Sometimes I wonder how we can have all this iron and no precious metals. The gold and copper are all to the east 60+ miles. I guess the iron deposits are sedimentary limestone and sandstone deposits, and the gold, silver, copper and rare earths are metamorphic veins and the placer deposits of breakdown stream accumulations of those. That black vein 40 miles south of hear is on the border of gold territory, there is probably some panning to be done there, right?

 

[Dave J.]

Some reality checks:

Atomic weight of iron is 55.8
Atomic weight of oxygen is 16.0

Therefore molecular weight of magnetite is 231.4
Percent of iron in magnetite is 72.3%

Therefore molecular weight of hematite is 159.6
Percent of iron in hematite is 69.9%

******************************************

The highest grade ores run in the 65-70% range. Almost impossible to get past 70% because of contaminants such as manganese, titanium, calcium, silica, aluminum, excess oxygen producing ferric iron, sulfur, and water of hydration of ferric oxides. Iron does occur in higher concentration as free iron and as wustite (FeO) but in specimen quantities, almost never on commercial mining scale. Magnetite rock is an important ore but even that usually runs in seams or lenses only a few feet in thickness.

Of rock types that are extremely common and also high in iron, that would be the basalts which typically run 1-4% magnetite by volume (iron by weight roughly twice that). Ultramafics with higher iron content are not rare, but in terms of percent of land parent material available for soil formation they don't amount to much. The ultramafics that go beyond ordinary basalt in iron content are of interest primarily because of their frequent association with valuable minerals, including iron itself if in high enough concentration.

Soil formation processes in many climates tend to concentrate iron in the soil by leaching out other elements, but in temperate climates in most cases the leaching processes tend to favor the retention of silica and single-layer silicate clays and aluminum oxide, the resulting concentration of iron in the soil not usually exceeding 7-20% even when the parent material is ultramafic rock. In the humid tropics, leaching processes are more extreme and if the conditions do not favor leaching of iron in preference to aluminum the result can be soils exceeding 20% iron content. The other "end product" is bauxite, a white oxide clay which is the ore mined for aluminum production.

Culpepper dirt is a temperate zone Ultisol, but not a tropical Oxisol. As noted in an earlier post, the clays tend toward kaolinite. Given the reported ultramafic parent material, the reported kaolinite silicate clay, and the weathering conditions, the iron content of the soil is probably within the range of 7 to 20%.

Thank you, Gunnar, for starting this thread.

Regarding the magnetic properties of the aforesaid iron content, "no comment".

--Dave J.