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I am finding surprisingly little information about this. I imagine that the process is somewhat like foliation except because the particles that go into marble (to my knowledge) don't have any noticeable elongation you get more amorphous billowing shapes rather than more regular layers. Any more details on this?

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EDIT: Or does it have something to do with the magma intrusions that contribute to the marble formation process?

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    $\begingroup$ Marble is a calcite (calcium carbonate), a type of sedimentary rock, that is heated and subject to fairly high pressure. It is not igneous. I suspect the marbling comes from the different deposition layers as they're laid down, and deformation from the subsequent pressure and heat. I'm not including this as an answer, because I'm not positive; this is more of an educated guess. $\endgroup$ – BillDOe Jul 21 '15 at 23:35
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    $\begingroup$ The general answer is that swirls and veins in marble are formed by a both primary (sedimentary) and secondary (metasomatic and metamorphic) processes. Can you add a photo of the types of features you are referring to? $\endgroup$ – geordie Jul 22 '15 at 0:07
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    $\begingroup$ Slight correction: Marble is a metamorphic rock formed from limestone, which is a sedimentary rock. Just wanted to clarify. $\endgroup$ – BillDOe Jul 22 '15 at 5:16
  • $\begingroup$ When I referred to magma intrusions, I meant those not directly touching the site of marble formation but presumably adding heat to it by proximity. They were mentioned in my textbook. Here is a photo for an idea of what I mean: themarbleguy.com/images/pillars.jpg $\endgroup$ – readyready15728 Aug 2 '15 at 18:11
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What you see in marble are not veins (for example in the picture of yours). By the term vein in geology we mean a magmatic intrusion in the rock in the form of vein. Can a marble have magma real veins? Yes. The process is explained here: https://en.wikipedia.org/wiki/Intrusive_rock The 'veins' you are referring to are coming from the different beds of the rock formation. Beds form by the deposition of layers of sediment on top of each other and they might have variations in mineral composition. As BillOer mentioned already, marble is a metamorphic rock formed from limestone. Can I have different type of 'veins' and swirls in the metamorphosed limestone in comparison with the initial limestone? YES. Why? Because during the metamorphic phase, pressure and heat is applied to the rock. So, we might have a partial melt and re - crystallization, a pressure slide forming swirls and new 'veins'.

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  • $\begingroup$ Veins are not necessarily magmatic. Especially in metamorphic rocks, most veins are actually hydrothermal. $\endgroup$ – Gimelist Jan 13 '16 at 3:55
  • $\begingroup$ You are right, I used Greek terminology in my mind! $\endgroup$ – Vasileios Antoniou Jan 14 '16 at 9:57
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particles that go into marble (to my knowledge) don't have any noticeable elongation

Not necessarily. Marble is mostly made of either calcite (CaCO3) or dolomite (CaMg(CO3)2), both of which are carbonates that do not exhibit any foliation in metamorphic rocks. But marble is rarely pure and commonly has some clays or other minerals that can contribute to any linear features. Notice that the stuff in your picture is quite big - you can have thin layers of not-pure-marble between the pure marble.

does it have something to do with the magma intrusions that contribute to the marble formation process

Marble forms by several processes, not always related to a magma intrusion. Marble forms by heating of carbonate rocks. It could be magma and it could be other stuff.

That said, marble can definitely have veining. More commonly the veining is the result of hydrothermal fluids, that is mostly supercritical water flowing through the rock (in veins), dissolving some minerals and precipitating others.

Sometimes you can have textures like that even without any minerals that can be foliated at all. If you take interbeds of calcite and black sand (quartz + heavy minerals, let's say magnetite) and start deforming it, you will get interesting textures. Go to Google Images and type in "metamorphic deformation".

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