Joined: Wed Jan 14, 2015 3:52 pm Posts: 576 Location: N Dakota
Well the trip was fun, but agates were scarce. Looks like the place has had a lot of traffic since I was there last. Sally still found a nice piece again. Girl has all the luck! So the next trip in September we plan to run the kayaks down the Yellowstone and hunt the gravel bars. We even made friends with a fellow from Glendive. Geologist, paleontologist, rock shop owner. He plans to run the river with us. More local knowledge is awsome.
Joined: Wed Jan 14, 2015 3:52 pm Posts: 576 Location: N Dakota
So this threw me for a bit of a loop. I was showing Timur the little pulse jig and ran a 5 gal pail of gravel from the creek we hunted agates on. Really nice gravel beds sitting on heavy clay bed. A prefect trap for gold! Instead of gold I found the typical garnet sands. Or so I thought. It was reddish in overall color but I decided to look at the fines under a microscope. I found very distinct clear green, red, pink, salmon, clear(white), pieces of crystal. None of it has any xtal form, just broken bits. But only in the very fine heavy sands. Absolutely none in even the slightly larger sand. I dont quite understand this, and almost zero black sands. I would think if its in the fines, larger pieces should show in the coarser gravels as well. No idea of what it might be other than garnet, quartz, maybe some topaz, but the green? Demantiod garnet? It could all be garnet, but not a single crystal to even give a slight clue. Small doesnt even begin to describe it. A straight pin looks like a baseball bat trying to push marbles at 10x small. A trip 5 miles up the creek may yield some larger materials or not, hard to say at this point. but it looks as if the valley goes at least 10 miles. So another trip.
Joined: Wed Jan 14, 2015 3:52 pm Posts: 576 Location: N Dakota
I've got a hunch the microscopic xtals are kimberlite indicator minerals. They match descriptions and colors almost perfectly. Kimberlites and lamporites are both found in the area. some very small diamonds have been found as well. The question I have is how far from a pipe will they travel? If Im finding almost all of them I would assume we are relatively close. There are some interesting possibilities that go with this. But knowing not all pipes or dykes produce diamonds I should be looking for larger specimens of gems. The green olivine, garnets, diopside, serpentine. what else?
Joined: Wed Jan 14, 2015 3:52 pm Posts: 576 Location: N Dakota
Small surprise in the microscopic sand xtal sample I found a half crystal of sapphire, absolutely beautiful with growth layers. clear almost colorless. And next to it one with a garnet inclusion? tiny red dot. Pulled them out and separated some other xtals of different colors trying to verify what they might be. Then I found a garnet cluster that contained all the colors except the green white and pink. So that explained the red, orange, salmon, amber mix all in one shot. The clear appear to be quarts (milky), agate, and at least 2 sapphires. Greens have 2 colors, dark almost black translucent, and yellowish green transparent possibly peridot. Pink I dont know, it is certainly vivid pink maybe rose quartz. Then there is the mix I usually see in my gold pan of iron, cinnabar, lead shot from hunters. So as a curiosity the sand is great. It also proved my pulse jig works in the field. however Sand is a problem still locking in my jig tray. That says I must run at least a double classifier screen. one for the large, one for the sand and run whats left in the middle.
Very neat! Small pink grains tend to be garnet. Rose quartz (and pink quartz for that matter) are never going to be saturated enough to show pink in sand grains. The sapphires sound very intriguing! I hope you'll have the time to investigate some more and keep us updated!
Joined: Wed Jan 14, 2015 3:52 pm Posts: 576 Location: N Dakota
The kayaks were the way to go. Took about a 6 mile float trip with Tom in the lead. Bounced from gravel bar to gravel bar until dark. Found lots of agate up to 2 lbs apiece. Even found something like an ammolite in a concretion. Some kind of clam. But I broke it. Agates were fair quality for the most part only a couple of top quality but a really fun trip regardless. Biggest surprise was the Mighty Yellowstone river was only deep enough for one sack of rocks in my yak. Sally put hers in the back of mine for awhile and I kept getting stuck. So I made her carry her own rocks. LOL!
Joined: Wed Sep 02, 2015 10:52 pm Posts: 1131 Location: Central Queensland, Australia
Dan&Sally wrote:
The kayaks were the way to go. Took about a 6 mile float trip with Tom in the lead. Bounced from gravel bar to gravel bar until dark. Found lots of agate up to 2 lbs apiece. Even found something like an ammolite in a concretion. Some kind of clam. But I broke it. Agates were fair quality for the most part only a couple of top quality but a really fun trip regardless. Biggest surprise was the Mighty Yellowstone river was only deep enough for one sack of rocks in my yak. Sally put hers in the back of mine for awhile and I kept getting stuck. So I made her carry her own rocks. LOL!
You know you've had a really successful fossicking trip when your kayak sinks as you try to take it all home
Better than mine yesterday - all I got were blisters, a sore back and maybe one small faceting stone Some days are diamonds and some days are dust.
Felt a bit knocked around as well - the pleasant digging weather is over here and the heat and humidity are starting to return. Might be time to get myself one of those ice vests, great for someone silly enough (like me) who wants to keep exerting themselves in the heat.
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