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I was really surpised to see that strontium is apparently more common than sulfur in the earth's crust, since it occurs in what I thought were pretty rare minerals.

Sulfur which seems to be everywhere such as in volcanoes, in the atmosphere as sulfur dioxide, in coal deposits, and is even found elementally in large lenses.

Sulfur seems to be ubiquitous. For example, fool's gold, iron pyrite is iron sulfide and it can be found in practically any stream bed. I would be hard pressed to find strontium in my local stream beds. And, of course, this sulfide is only one of many commonly sulfides.

Is strontium really more common than sulfur? It seems implausible. What is the basis for this claim?

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    $\begingroup$ Related question on Physics SE: physics.stackexchange.com/questions/1918/… . Also, the Earth Science SE might be a better place for this question. Note there is a large distinction between elemental distribution in the crust, and in other layers of the earth. $\endgroup$ – Jon Custer Apr 15 '16 at 15:18
  • $\begingroup$ This section of a Wikipedia article on the abundance of the elements has a nice graph of the mass abundance over the universe en.wikipedia.org/wiki/… and this section has a nice table of overall abundance on earth You can look at both mass abundance and abundance by number of atoms en.wikipedia.org/wiki/… $\endgroup$ – MaxW Apr 15 '16 at 16:29
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    $\begingroup$ The overall earth abundance of S is 6350ppm by weight, and for Sr 13 ppm. $\endgroup$ – MaxW Apr 15 '16 at 16:39
  • $\begingroup$ It worth to distinguish abundance from "easy to find". Many elements can be found in enriched sources even if they are rare in average. E.g gold is a very rare element, yet it is relatively to mine as it is concentrated in given geological formations. $\endgroup$ – Greg Apr 16 '16 at 15:03
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The primary reason for this and other seemingly implausible features of element distribution is this: some elements are concentrated, and some are scattered. Strontium is much like calcium (which is way more abundant) and can hide as a tiny admixture in its minerals, while sulfur is pretty much on its own.

Just think of the rare earth elements. Their name is in fact a misnomer; they are not rare at all, just very scattered and thus difficult to come by, hence the relatively late discovery. On the other hand, silver and gold, which are thousands times less abundant, were known since antiquity (or probably before that).

Also, you see yourself that there are several columns with the same name "Abundance in crust", and the data for the same element vary quite significantly between the columns. This is due to the fact that finding an element's content in the crust is not easy at all. Wait, don't they say explicitly that the numbers are but estimates?

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    $\begingroup$ I'm sure that you're exactly right. I was an analytical chemist specializing in x-ray fluorescence. All Ca containing compounds will have the other Group 2 elements as well. (Really a wonderful confirmation of utility of the periodic table.) So massive amounts of $\ce{CaCO3}$ in the crust means a fair amount of Sr in the crust as well. $\endgroup$ – MaxW Apr 15 '16 at 16:39

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