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Questions tagged [mineralogy]

questions relating to the scientific study and identification of minerals.

13
votes
1answer
24k views

What are the high field strength and large ion lithophile (HFS or HFSE & LIL or LILE) elements?

There are two groups of elements that are frequently mentioned when discussing incompatible trace elements. They are the high field strength elements (HFS or HFSE) and the large ion lithophile ...
20
votes
2answers
2k views

In what geological situations can I find gold?

I've heard that gold ore is often associated with quartz veins. What geological processes enable gold particles to naturally cluster together like this? What characteristics/properties should I look ...
13
votes
5answers
17k views

Why do gold deposits form only in certain areas of the earth?

In the map above you can find that most elements are spread evenly throughout Earth's crust and that they are available all around the Earth. However, gold can only be found in certain areas of the ...
30
votes
3answers
7k views

Why do felsic materials have lower melting points than mafic?

It is clear from Bowen's reaction series that more felsic minerals have lower melting points than mafic minerals. As far as I know, the same is true of quenched glasses. Felsics have a higher degree ...
3
votes
1answer
781 views

What are the implications of the recent discovery that huge oceans exist close to the mantle of the Earth? [duplicate]

I was of the notion that as we get deeper into the Earth, it gets hotter and hotter. If so, how can there be huge oceans (they seem bigger than our Pacific) exist at such a place? If so, what are the ...
18
votes
2answers
2k views

What are these metallic nodules that were found at low tide on the UK south coast?

Smooth spherical crystalline metal nodules Outside and inside surface does not scratch with a knife blade Inside lustre brassy, radially striated metallic crystals radiating from a lumpy centre at the ...
15
votes
2answers
14k views

Why does the colour of amethyst fade if exposed to too much light?

It is well known that the purple hue that is characteristic of the amethyst quartz ($\ce{SiO2}$) will fade if the crystal is exposed to light for a prolonged period of time. What is the underlying ...
5
votes
2answers
257 views

What is serpentinization, in the context of disappearance of surface water on Mars?

The recent paper in Nature The divergent fates of primitive hydrospheric water on Earth and Mars (Nature 552, 391–394 (21 December 2017) doi:10.1038/nature25031) has been linked by many recent news ...
9
votes
1answer
334 views

How does the composition of volcanic rock change as it makes its ascent towards the surface?

A schematic for the fluid mechanics of a volcano is represented below. Graciously borrowed from Figure 1 of the reference cited below From the caption of that figure: During explosive eruptions, ...
7
votes
1answer
349 views

Mineral Rock Identification

Went out hiking after some heavy rains and came across an area that looked like broken glass sticking out from mud. On a closer look this is what we found. Not sure what it is and would like to know ...
6
votes
1answer
196 views

Are there probably decent oil fields located in the middle of the ocean?

I did a google image search for a world map of offshore oil. Surprisingly I found virtually nothing. I had to search country by country for such maps. I noticed most if not all were located very near ...