Talk:Igneous rock

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Can someone help me out with the geological definition of dike at dike? Extend it to a dike (geology) page if you like... Thanks. dave 17:19 16 Jul 2003 (UTC)

Done - or at least started. Dike (geology) --Vsmith 03:19, 11 Sep 2004 (UTC)

The part on classification is pretty inadquate. Without having to totally rip off something else, we should at least either a) move it to a new page such as Igneous rock classification and give it a good go, or at least condense the wisdom in the first part of this. For instance, the current spiel focuses on poor but serviceable definitions of igneous rocks based entirely on whether they are felsic or mafic, without giving any regard to the chemistry (except the TAS diagram, which is a last resort anyway).
For instance there is no way to get stuck into the taxonomy of rocks in an organised manner, such as in that flowchart. There are principles to the taxonomy of igneous rocks after all. Even taking aside the fact it's a human endeavor, there are some rocks such as alkaline basalts, peralkaline and ultrapotassic rocks which are distinct solely because of their mechanism of melting - for instance thermal divides, etc. created by partial melting mechanisms. And there's the lack of a definition between calc-alkaline and tholeiitic. Rolinator 05:25, 28 December 2005 (UTC)


Be nice to see some citations for estimated temperature ranges of magma.

Thangalin 01:40, 23 October 2006 (PST)

B class[edit]

Well written article, but I'm reluctant to give it better than a B class rating for "WikiProject Geology" until the references are actually cited in the text so we can see where statements came from. --Zamphuor 15:52, 22 April 2007 (UTC)

Nice job. yesterday I added 2 sentences on the extrusive and intrusive igneous rocks. Glad to see someone worked on it. —Preceding unsigned comment added by Jwebbxsjado (talkcontribs) 14:29, 25 September 2007 (UTC) hey my name is shuhieb im doing a project can you guys help me —Preceding unsigned comment added by (talk) 03:01, 5 April 2011 (UTC)


I'm a casual user that noticed some vandalism on the page. I'm going to remove it, but I noticed in the history that this page has had a fair amount of vandalism for some strange reason. Someone a bit more saavy with the workings of Wikipedia might want to do something about it. —Preceding unsigned comment added by (talk) 16:00, 20 October 2007 (UTC)

Ok, I have tried removing it, let's see if it remains successful. TrondBK (talk) 17:26, 26 December 2010 (UTC)

Porphyritic classification[edit]

Something along the lines of:
Porphyritic rocks are classified as either phaneritic or aphanitic according to the groundmass' texture. Further refinement to the classification is made by adding the adjectives porphyritic or porphyry to the name (i.e. porphyritic andesite or andesite porphyry.)
should be added to either this page or the pages on porphyry and porphyritic texture. Zappa2496 (talk) 07:28, 21 April 2008 (UTC)


the ingeous rock history is cool but the most important subject that relates to that is my science class who is studing that and my teacher he has many things to do with that —Preceding unsigned comment added by (talk) 19:49, 8 September 2008 (UTC)

Errors on page[edit]

at the top of the article it says taht igneous comes from the latin work ignis, but at the bottom it says it comes from the latin work igneus. This needs to be fixed Wumbla (talk) 03:05, 17 November 2008 (UTC)

i want to know the ten examples of igneous rocks

HEY!!!!!!!!! —Preceding unsigned comment added by (talk) 21:59, 3 March 2009 (UTC)

ERROR HERE: "melting is caused by one or more of three processes: an increase in temperature, a decrease in pressure," SHOULD BE "increase in pressure" NOT "decrease in pressure". Preceding unsigned comment added by 17:36, 24 October 2016‎ (UTC)

Decrease in pressure is correct. It refers to the process of decompressional adiabatic cooling of rock as it rises. This reduction in pressure with decreasing depth, with or without a decrease in temperature, melts the rock to form molten magma. For more details see, for example, for an explanation and for the physics and mathematics details. GeoWriter (talk) 20:52, 24 October 2016 (UTC)


First section of this article has been vandalized with crude sexual humor. I'm not sure how to fix this problem.

Also found that when I clicked on the sandbox, a lude illustration came up. —Preceding unsigned comment added by (talk) 00:09, 29 May 2009 (UTC)


"igneous rocks can be either intrusive (plutonic), extrusive (volcanic) "

Intrusive/plutonic and extrusive/volcanic are not synonyms! A near surface lava sill is volcanic, but it is not extrusive. A dyke is intrusive, but it is not plutonic. —Preceding unsigned comment added by (talk) 08:36, 21 November 2009 (UTC)

Classification Chart[edit]

Do you think this chart would be proper for the page?

There is also one for sedimentary and metamorphic. Andrew Colvin (talk) 00:07, 4 January 2010 (UTC)

the igneous rock has other rocks such as:granite,basalt,obsidian,pumic. — Preceding unsigned comment added by (talk) 22:06, 25 October 2011 (UTC)

proportion of crust[edit]

I tagged the statement that 95% of the crust is igneous and the rest metamorphic or sedimentary. That seems dubious to me - are any rocks at a depth of several km igneous? I can't access the page that is cited, but I can access this page, which says that 90-95% of the crust is igneous and metamorphic. RockMagnetist (talk) 16:09, 19 March 2012 (UTC)

Just checked my copy of the Klein book and the content is verified, however on page 475 rather than 275. Methinks I may have added that and must have typoed the wrong page (or someone changed it ... naw, surely not :) Having done that, I would agree that your source and content looks more reasonable - I'd support the change. Vsmith (talk) 17:59, 19 March 2012 (UTC)

Acidic/Basic Felsic/Mafic[edit]

If I recall correctly old terms for Felsic, Intermediate, Mafic and Ultra Mafic were Acidic, Intermediate, Basic, Ultra Basic. It looks like the Felsic article mentions it


In modern usage, the term acid rock, although sometimes used as a synonym, refers to a high-silica-content (greater than 63% SiO2 by weight) volcanic rock, such as rhyolite. The term was used more broadly in older geologic literature. It is considered archaic now, as the terms "acidic" and "basic rock" were based on an incorrect idea, dating from the 19th century, that silicic acid was the chief form of silicon occurring in rocks.

but I'd have thought there should be a mention somewhere on this page, and I guess it needs a reliable source too. EdwardLane (talk) 02:00, 21 April 2012 (UTC)

Strength of rocks[edit]

I think this section should be added or similar that talks about the physical characteristics of rocks. RonRodex (talk) 01:09, 12 May 2012 (UTC)

solidification not crystalization[edit]

I came here looking for a reference to stick into the Volcanism#Forming_rocks section (it probably ought to be called lithification but that rather interestingly redirects to diagenisis with no mention of solidification of igneous material), but I see lots of unsourced bits in this article. I don't doubt they are likely to be correct but I had thought igneous rock was formed by the 'crystalization' of magma/lava - but the lede here says

Igneous rock is formed through the cooling and solidification of magma or lava. Igneous rock may form with or without crystallization, either below the surface as intrusive (plutonic) rocks or on the surface as extrusive (volcanic) rocks.

There might be a suitable reference in rock (geology)#Rock_classification but it's to a book, so harder to check. Solidification seems safe to use I agree, but are there igneous rocks that are not crystaline? Is it volcanic glass we're talking about or have I missed something else obvious? I'll change the volcanism article to say cools and solidifies (as that seems a safe short term solution). The rather stubby Formation of rocks looks to have the same issue (saying 'crystalised' from a magma/melt) using a reference from encyclopedia brittanica. EdwardLane (talk) 11:49, 7 November 2012 (UTC)

Proposed External link - The IUGS systematics of igneous rocks[edit]

There is some kind of protection on the article and I cannot edit it. Can anyone else put this in the "External links " section? The IUGS systematics of igneous rocks It can also be used to source a bunch of stuff in the article. KatieBoundary (talk) 01:31, 13 March 2013 (UTC)

Done, seems good short term but I guess we should just be expanding the article based on that source in the long term. EdwardLane (talk) 17:52, 13 March 2013 (UTC)

Don't get classification scheme chart[edit]

I don't get at all the chart, "basic classification scheme for igneous rocks based on their mineralogy". The chart has a Y axis labeled with "vol% of minerals". The caption is no help since it says:

If the approximate volume fractions of minerals in the rock are known the rock name and silica content can be read off the diagram.

So does that mean that a rock can have "0% minerals" and simultaneously be composed of the minerals, amphibole or olivine? Well, that's what the chart appears to be claiming. -- KarlHallowell (talk) 17:01, 28 November 2013 (UTC)

The scale indicates the percentage of each mineral in the overall rock. It always adds up to 100%, which is why the overall diagram is rectangular. The coloured areas within the diagram indicate the proportions of each constituent mineral – the height of each curved stripe (when read on the % axis) indicates their proportion. Andy Dingley (talk) 01:13, 29 November 2013 (UTC)


This page is in serious need of references. Chestmas (talk) 17:31, 2 May 2015 (UTC)