# Placer diamonds



## Seamus (Aug 10, 2008)

Has anyone found placer diamonds in Washington state. I'm not asking for any location secrets. Just wondering if anone has found any.


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## NuggetHuntingFool (Aug 10, 2008)

If there are any Kimberlite pipes in your area then there should be some diamonds near them. Not always the case but those are the geological formations that are most often associated with diamonds.


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## Seamus (Aug 11, 2008)

I found some olivine and serpentine in one hanging valley. Right over the hill is a creek that the old timers (from the eighteen eighties) had some crystals assayed that turned out to be industrial grade diamonds. Olivine is an ignious rock that forms in these pipes. Serpentine is an olivine that turned metamorphic. 
That's why I was wondering if anyone found diamonds here in Washington.
Just wondering, curiousity. I found placer diamonds in New Zealand a few years back. Fun.


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## Seamus (Sep 5, 2008)

If there is no interest in diamonds, then how about garnets and other gem stones in your placer mining. I have found garnets in several places here in Washington state. The placer gravels get red with busted up garnet crystal sands and a few pickers once in a while. I surch for the source up stream and get some nice stones. Oouuuhh, I'm ready to go back out digging. How about you?


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## NuggetHuntingFool (Sep 15, 2008)

There is a guy on YouTube that hunted diamonds in Washington I believe.

Search "Finding Gold" and watch the episodes. Pretty good info.
I think he also finds opals in Washington State as well.


Regards!


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## Shecker (Sep 15, 2008)

There is an easy way to tell is diamonds are present in a placer deposit. Rub Vaseline on the bottom of a gold pan. Diamonds stick to Vaseline. A few other things will stick as well, but this is still a good and simple prospecting technique.

Randy in Gunnison


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## Anonymous (Sep 16, 2008)

Seamus when your prospecting bring your microscope along to investigate the heavies in your gold pan.

http://www.landandminerals.com/diamond_indicators.html


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## Seamus (Sep 16, 2008)

As a rock hounder I read up on indicaters for kimberlites and lamproites where diamonds come from. I know some of the associated minerals and found a serpentine cliff with olivine. A mile over the pass from where this serpentine, is an area that the old timers (1880's) supposedly found industrial grade diamonds.

I carry a twelve power loupe with me always (thanks Gustavus).

I knew about diamond mines in Africa greasing there plate to catch diamonds. Now I will add vaseline to my prospecting kit (thanks Shecker).


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## Seamus (Oct 16, 2008)

I did some sluicing in Sauk Creek down stream from Monte Cristo,Washington a month ago and found a dozen industrial grade diamonds (tenth of a carat). One about a quarter carat in size.

The old timers were right to have the quartz crystals tested. I'm saving them as a keepsake and story telling rather than monitary reasons. It's the precious metals (gold silver) that I'm getting for profit.

I used classifiers to size the gravels and vaseline in my pan to save the diamonds.

There are several igneous formations in the area where the diamonds come from. If you prospect near these type of formations, then it would be a good idea to save quartz type crystals for examination to see if there diamonds. 

Happy hunting and I hope your equipment fills up with PMs, and maybe even diamonds.


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## GrantS (Sep 28, 2019)

Seamus,

Could you please send a photograph of the diamonds you found?

Grant


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## butcher (Sep 28, 2019)

Seamus last visited the forum in 2012


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## cacarr (Jan 18, 2020)

NuggetHuntingFool said:


> If there are any Kimberlite pipes in your area then there should be some diamonds near them. Not always the case but those are the geological formations that are most often associated with diamonds.



I know this is an ancient thread, but looks like it still ranks high for "diamonds Washington" searches.

I'm not aware of any kimberlite diatremes in Washington. If there were any, I suppose they would be located in extreme NE Washington, closer to cratonic lithosphere. The rest of Washington is all various terranes that accreted to the NA continent. 

Diamonds found in Washington aren't coming from the same source as most commercial diamond mines -- the geology is not right for that. They are subduction zone diamonds, and their source is not super well understood as far as I can tell. They are either hosted in ophiolite slabs (in more or less serpentinized peridotite), probably very widely disseminated, or they were sampled at depth and brought near the surface by various lamprophyre-type mafic or ultramafic intrusions (dikes and sills, etc), or both.

There are ophiolite sections in the Northern Cascades, but IIRC, not in the south -- and I've heard of placer miners finding the very occasional little diamond not that far north of the Columbia River, in addition to up in the Northern Cascades. 

Subduction zone macro-diamonds seem to be a lot *more* common in the Klamath Mountains of California and SW Oregon, and in the northern Sierra Nevadas -- frequently in placers downstream from serpentinized peridotite, often in association with platinum group metals and chromite. 

My guess is that they are both hosted in oceanic upper-mantle slabs that got obducted up onto the continent, and also erode out of lamprophyre pipes -- sampled at depth, possibly from subducting slabs carrying a lot of carbon that got stuck in a diamond stability zone, so that the diamonds didn't just turn into graphite as the slab continued down into hotter zones.


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