Talk:Placer deposit

Untitled
I always wondered where Placer County, California got its name. Given the Gold Rush history in Auburn, it is pretty clear this is why.

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Edits
"There are heavy silicates, such as amphibole and pyroxene, that will collect in extensive placers where they comprise the country rock. "

I am not sure exactly what this is meant to say? Its like saying granitic sands aggregate over granite plutons.Rolinator 09:54, 14 October 2006 (UTC)

Placer Gold (Au) Accumulation
Logic says in syllogism - that if water flows downhill over rock, then eventually, the precious metal or mineral will wash down to the valley. Further, if the matter (gold & mineral) is heavier than water, then force and gravity will distribute the matter. Force (water current) will push the matter down the path of least resistance. Gravity will attract that matter to the centre of the earth. Therefore, matter is washed from the hills to the centre and sides of the water-flow. Stream tests (MacKay, B. R., Cdn Geol. Survey Mem. 127, p. 65, 1921) have proven that sediment will gather at the bend in the water-flow but (gold) accumulation in the centre of the stream is just Baer Law theory. Rodeney (talk) 14:49, 31 August 2008 (UTC) Rodeney


 * I presume you are quoting Emmons 1937 Gold Deposits of the World here. Please attribute your sources. Also, this is the talk page of the article - so are you proposing an addition or what? Vsmith (talk) 15:34, 31 August 2008 (UTC)

Diamonds
"The source of diamonds are kimberlites." — Preceding unsigned comment added by Cacarr (talk • contribs) 05:03, 27 February 2020 (UTC)

Kimberlite is not the sole source of all diamonds, and not even the sole source of all economic placer diamonds. Lamproite is the source of some economic placer deposits -- e.g., the Smoke Creek placers from the Arglye lamproite pipe, Australia. Diamonds can be hosted in ultramafic lamprophyre dikes as well, though I'm not aware of any being the known source of economic placers. And it should be noted that some commercially significant alluvial deposits have unknown sources -- e.g, the Kalimantan diamond placers show no indication whatsoever of kimberlite or lamproite. Additionally, economically insignificant micro-diamonds have been found hosted in ophiolitic peridotite, and such ophiolitic rock is a candidate for hosting macro-diamonds of unknown origin in subduction zones -- e.g., diamonds found by gold placer miners in the Sierra Nevadas of California, the Klamath mountains of California and Oregon, and in northern Washington State.

Kimberlite is the most economically important host, but certainly not the sole source of all diamonds. — Preceding unsigned comment added by Cacarr (talk • contribs) 04:58, 27 February 2020 (UTC)