[Chemistry4me]

Why can a magmatic nickel deposit could not exist in a felsic host rock?

[Bass]

Nickel (along with chrome and pge) has an affinity for ultramafic rocks.  They form as immiscible minerals that accumulate due to their density in bands in the crystallizing magma (that is they rain down as discrete particles).

[Chemistry4me]

The thing is, I don't really have an answer.... []

[JimBob]

Hey dude - we are geologist - not chemist or even geochemist. Those guys are weird - really weird!

[Chemistry4me]

Okay dudes, how about: What occurs when a smectite mineral swells?

[Bass]

It gets a smec tighter []

[Bass]

Smectites are phyllosilicate clays (montmorrillonite, nontronite) composed of an octohedral sheet sandwiched between two tetragonal sheets.  (just thought I'd throw a little jargon out there- helps to keep the rifraff in the profession)

What that mouthful means is that, when water is added, the clay can absorb the water and trap it between the sheets, which causes swelling.  Water is lost between the sheets as conditions turn dry, allowing shrinkage.

[JimBob]

It becomes FURTHER hydrated. Water in the interstitial spaces of this phyllosilicate make it slick as greased owl sh1t.

Just what are you looking for C4 - some chemical reaction? Or do you wear cosmetics made of this stuff and are having problems when your face gets wet?

I can't help with that.

Will call later today, Bass

[Chemistry4me]

It was simply a geology question of the week (supposedly).

[CreativeEnergy]

Since I'm new here, I'm not sure whether or not the question has been answered. But in the event that it hasn't I offer this.

It is correct that the red color in sandstone is due to iron oxide. As for the patches of green, the primary minerals that make up sandstone are quartz and feldspar. Therefore, I would imagine that the green color is due to the alkali feldspar, microcline (KaAlSi₃O₈). But, I'm just guessing here.

[JimBob]

iron on the red and iron on the green, just different valences for the Fe.  Copper is a very small, remote possibility for the green. It is a very unusual possibility.

[katesisco]

I like Dr Ward's reference to this massive deposit of red soil in his African hunt for animals from the K/T die off.  He looks around and it is red everywhere.  And he is not high in elevation; it is oxidized iron.  The seas had receded although he doesn't state how far, I propose as low as only a couple miles of water from the sea bed up.  If one was to seriously consider that our E is circled N and S of the Equator by plasma as NASA proposes, then it is not inconceivable that the seas experienced massive beyond thinking electrical charges ala Birkeland current and that this charge separated the contaminants from the water.  The result of course, would be pure water but incomplete from the point of view from all living creatures which need minerals to survive.  It may have begun farming and cattle raising for the protein and the never-ending war for possession of surface water ala Jericho and its ever-flowing spring sufficient to wash the accumulation of salts away.  A prize fought over ever since. 

[JimBob]

How do you tell the hardness of a rock? What is a streak. And why are these two things important in identifying rocks?  How do you figure out these two properties?

[Osogovo]

How do you tell the hardness of a rock? What is a streak. And why are these two things important in identifying rocks?  How do you figure out these two properties?

is streak dust for lab testing? do the same tests for minerals apply for rocks too [1]