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Identity HelpTellurides? Cid mining district (Silver Hill area) NC USA
29th Jul 2014 23:37 UTCRohde Rubble
Color: White --→ Gray ---→ Yellow
Streak: Varies with color but relative to
Hardness: 2.5 or lower (scratched by fingernail)
Dimensions: ~ 9cm x 9cm (main crystal structure app. 2.5 cm x 2 cm)
Locality: Cid Mining District, Davidson Co. , North Carolina, USA --- from Silver Hill Mine app. 10 miles nne as the crow flies
Optical: Highly anisotropic
These samples were found within a 20 foot zone in a metamorphic carbonate matrix that grades from predominately calcite -→ dolomite --→ ankerite --→ secondary enrichment (quartz dominated) --→ oxidation zone. Substantial evidence of mineral leaching, and reconcentration.
Other minerals collected in this vein: Garnet, quartzite, silver, galena, pyrite. The small area these were collected show a regional contact zone particular to the whole structure with a layering of minerals otherwise well sorted in a typical carbonate dominated metamorphic series. Slight saddling curves of carbonate minerals most apparent in dolomite.
The focus is on the mineral in the center of the matrix which may be flattened or worn by weathering, being found at or near surface level. No reaction to HCL other than slight etching host material. Nitric acid testing was inconclusive (going from 10k to 18k). Images 1 and 2 of same sample, image 3 of another which has a looser less defined structure.
29th Jul 2014 23:54 UTCRohde Rubble
Image 1: 9cm x 4cm
Image 2: 8cm x 5cm
Image 3: 15cm x 10cm
My hope: Image 1: Calaverite with AU -------------- Image 2: Calaverite ----------- Image 3: Silver, sylvanite, pyrite, and quartz in limonite
30th Jul 2014 00:06 UTCRohde Rubble
30th Jul 2014 00:40 UTCReiner Mielke Expert
30th Jul 2014 05:15 UTCRohde Rubble
On a geologic note, this area I have collected has been very good to learn basic geology because I get to study this vein from the granitic outcroppings where it emerges as a talc schist about 200 meters above the oxidation zone, all the way to its oxidized state, the creek gets blood red here from all the acids draining off such a large ore zone which alters very fast, into a small slow moving creek, (serious probably undocumented AMD problem here).... anyways
As I looked at my series of samples from the top down, I noticed the micas diminished, (biotite, roscoelite, and muscovite) The weathered rocks from the large granites have large well developed micas and small poorly sorted minerals. They can break with a karate chop! As the vein becomes more developed the micas get smaller and more brittle, as the minerals series replaces and alters becoming stronger under increasing pressure, and about halfway through there is very little to no mica in the oxidized zone.
I was studying about this series of enrichment, reading some old USGS bulletins which theorized sulfuric acids may have the ability, mainly in secondary or tertiary ore enrichment zones under localized pressure, to have dissolved, altered and redeposited the . This playing a possible role in the formation of telluride compounds. Is this true? If memory serves me this was an old bulletin from the 1920's...
Also saw one of the few telluride localities in the world listed on MD DB, is right here, next to yours truly, in Montgomery Co. Who's to say though?
Sorry if that is too wordy but I just wanted to parlay my observations, not trying to softpeddle anything that isn't there to begin with:-D Learning is the big payoff, no matter what I have found some nice garnet and quartz boxworks.
Can anyone recommend a good service to get this analyzed properly? Would I have to get some concentrates analyzed by the tried and true fire assay, or can x ray scans determine this data quality.
30th Jul 2014 14:13 UTCReiner Mielke Expert
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Copyright © mindat.org and the Hudson Institute of Mineralogy 1993-2024, 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.
Privacy Policy - Terms & Conditions - Contact Us / DMCA issues - Report a bug/vulnerability Current server date and time: March 28, 2024 16:46:49