What Am I Seeing In This Mineral Specimen?

[Lesgold]

Hi Folks,

My good mate Joe and I went out to have a look at some old hard rock gold mines in the local area. It is an area of prospecting that we don’t have any knowledge of and we are hoping to get a bit of advice from the geology wizards on the forum. 
 

We went out purely for a “look see” and try to make some sort of sense of what happened in this area in the past. We took our 6k’s with us just in case there was a scrap or two of gold to be found. This particular area was littered with old mines that produced gold, silver, lead and zinc over an extended period of time. It was granite country and the host rock was hard and difficult to break. Mullock piles were littered with decomposing granite, soil and piles of solid granite rock. We ran our detectors over the heaps and found the usual suspects. Lead shot, rusty steel, pieces of fine copper etc were distractions that showed up every couple of steps. For some reason, we were able to get faint signals off the occasional granite rock and just put it down to mineralisation. On one pile Joe and I got strong signals on rock pieces that had quartz veins running through them. The poor old picks took a beating as we tried to break the specimens down into smaller chunks. We knew we were on to something as the signals in the rocks were quite localised. As pieces were chipped away, they were tested for a signal on the detector. Eventually we were able to break one of the rocks in half directly through the quartz vein. Both halves sounded off on the detector. Here is what we saw. 

Can any of you tell us what we might be looking at? We have no idea and would only be guessing. If the geology experts could educate us we would be quite appreciative as we are keen to find an answer.

[Wild Bill]

Hi Lesgold, it looks like Antimony to me.  Do a search Antimony in quartz and check out images. 

Here’s a sample my prospecting partner is holding from a very high grade gold mine that produced Antimony.  I haven’t verified this through assays but it’s an Antimony producer in the past. 

[Wild Bill]

Keep in mind that if you do any crushing and furness smelting of Gold/Antimony ore that it is very toxic.  Ventilation and respirator is recommended.  
 

 

[Redz]

10 hours ago, Lesgold said:

gold, silver, lead and zinc

These mines very frequently produce a lot of galena (lead sulfide) which in a fresh break like you describe produce very silvery lumps like you have in the image. Over some time these oxidize black, and the ore often looks blackish.

The galena will melt quite easily into lead, but the fumes are not good.

Typically galena doesnt sound off much, but it can depending on impurities. If you crush the rock you will also probably get some free gold.

[Wild Bill]

Probably as Redz says.  It just looks remarkably like Antimony to me.  But Galena looks so similar.  If you live near a university with a geology department you can take a sample to them.  Since it’s a past producer of lead… it’s likely lead.  I got a bit narrowly focused on what it looks like but both lead and antimony requires caution.  

[Wild Bill]

Here’s where all those elements come together in one big happy family!  Gold, silver, lead, zinc, antimony and tin. 
 

https://pubs.usgs.gov/bul/b2064-jj/b2064-jj.pdf 

[GotAU?]

There’s a guy in AU advertising XRF analysis at $20AU per sample- that’s really the only way to ID it for sure as I think there are several possibilities based on looking at just that photograph.
 

https://www.geologynet.com/product/xrf-sample-analysis/?v=0b3b97fa6688

[Lesgold]

Thanks for the replies guys. That’s a good idea about taking the sample in for XRF analysis. I can get that done locally. Sold some gold jewellery recently and it all went under the XRF to determine purity and makeup. The sample in the photo above makes a beautiful sound on the 6000. As it is quite a pretty sample, I think it will be left intact. Here is another sample that made the detector react. When we broke the rock up, the signal was again confined to one piece.

[Wild Bill]

Lesgold, if you have it analyzed please let us know what the results are and thanks for sharing it.