Talk:Granite

From Wikipedia, the free encyclopedia

WikiProject Volcanoes

This article is part of WikiProject Volcanoes, a project to systematically present information on volcanoes, volcanology, igneous petrology, and related subjects. If you would like to participate, you can choose to edit the article attached to this page (see Wikipedia:Contributing FAQ for more information), or join by visiting the project page.
B This article has been rated as B-Class on the quality scale.
High This article has been rated as High-importance to WikiProject Volcanoes on the project's importance scale.
Assessment comments.
Earth sciences Portal
Granite is part of WikiProject Geology, an attempt at creating a standardized, informative, comprehensive and easy-to-use geology resource. If you would like to participate, you can choose to edit this article, or visit the project page for more information.
B This article has been rated as B-class on the quality scale.
Mid This article has been rated as Mid-importance on the importance scale.
Granite is included in the 2007 Wikipedia for Schools, or is a candidate for inclusion in future versions. Please maintain high quality standards, and make an extra effort to include free images, because non-free images cannot be used on the CDs.

Contents

[edit] Removed

Removed the following from the Uses: Antiquity section as it appears to be irrelevant to the article:

Nevertheless evidence indicates steel production in East Africa around 1400 BC (see [1] & Iron age: The Iron Age in Africa and India). The Iron Age in Ancient Egypt has been shown to have begun no later than 4000 BC (see Iron Age), and Egyptian ruler Tutankhamun died in 1323 BC and was buried with an iron dagger. Hardened steel has a Mohs hardness of 7 and up ([2]). Evidence of shipbuilding in Ancient Egypt dates to circa 2500 BC (see Ancient Egypt: Timeline of Achievements).
As footnotes, Professors Harrell and Lazzarini and Mr. Bruno (at E4, E16, I1, I12) also discuss ancient Egyptian works containing quartz and comprised of basalt (E15).

Vsmith 02:18, 21 Jun 2005 (UTC)

Removed dolerite as it is a mafic rock with little quartz and thus not harder than granite as was indicated. The reference given doesn't say that. In addition removed sentence about hardened steel, the Egyptians were in the iron age, but don't see a reference for hardened steel other than the uncertain material above. -Vsmith 02:37, 21 Jun 2005 (UTC)

See User:Mark Dingemanse/Roylee for more information on the strategy of the person who added this, and who is trying to edit a web of Afrocentric fringe theories and original research into Wikipedia. Any help welcome in screening the edits of this person. — mark ✎ 29 June 2005 13:34 (UTC)

Rejiggered this. Salient points for which I particularly would not like to see reversions:

  • It is inappropriate to use the Mohs scale of hardness to describe physical properties of rocks. This is for minerals only.
  • What is "an interesting proportion of plagioclase"? Bad wording; so I hunted out the QAPF diagram. Also, removed poorly worded unscientific stuff about "some proportion" of this and that, and the bit on monzonite being plag>orthoclase, because it's not; look at the QAPF diagram. Monzonite is <5% quartz.
  • Added in something on what granite looks like, and how it outcrops, etcetera.
  • Added in a section on granite emplacement mechanisms. Pretty basic, but I think that his issue deserves its own page anyway, for all plutonic rocks including ultramafic intrusions, etc.

Much better, I think. Rolinator 02:02, 26 January 2006 (UTC)

Removed a comment in the opening paragraph about granite cropping out as boulders in sandy soil matrix. That isn't a rock outcrop of granite, but rather a conglomerate with granite lithic fragments in it. That has little to nothing to do with the igneous processes involved... Although it may be worthwhile to discuss soils of granitic origin in terms of their sand and clay-mineral content. Snoop0x7b 00:32, 11 April 2007 (UTC)


[edit] Radioactivity

Given the widespread belief that granite is a potential source of radiation, I think it would be appropriate to include something on the subject. In the UK, for example, radon (from, as I understand it, granite in the earth) is a big problem in some areas. I don't feel I know enough about this myself, but here's something I ferreted out which may be helpful:

Although all rocks and soil contain radioactive elements, the proportion they contain varies. Granite, for example, is high in radioactivity because it contains more uranium than most rock-types. The result is that some people in the country receive many times the amount of radiation as others, merely by living in, say, Cornwall rather than in Oxfordshire.
... Uranium decays eventually into a nonradioactive form of lead, but not before it has formed a long succession of intermediate radioactive elements. One of these is the radioactive gas radon. Radon is the biggest single source of natural background radiation. It accounts for almost half of our average annual radiation dose.
Average annual radiation dose in UK — 1300 µSv
Add 5000 (on average) if living in Cornwall
Add 300 if living in a well insulated house with low ventilation

Source: Radioactivity and Radiation, from the UKAEA. — Johan the Ghost seance 15:43, 5 March 2006 (UTC)

In Australia, the aborigines avoid some granite plutons, and don't live on top of them. They say it's "sickness country". Oddly enough, these granites are some of the mosy highly radioactive in the world. Radon does come from granites, but not exclusively, as a lot of Proterozoic rocks can host weak roll-front uranium mineralisation, as can some forms of laterite, and some beach sands (those with high heavy mineral concentrations such as thorianite).
Is it worth putting a section into the granite page? Not really. It is more a function of soil than rock type; perhaps hunt round for an article on soil gas, basement or radon. For instance, while many people especially in tropical countries and warm climates live on granite, radon accumulation is only a problem in cold climates where house ventilation is restricted, or in areas where there are usually basements; the U.S. for example. In Australia, a huge proportion of the country areas are underlain by granite, but the climate is hot, favoring ventlated homes, and we don;'t have a penchant for basements.
If you want it, stick it in the see also section.Rolinator 23:33, 8 March 2006 (UTC)
Thanks for the info. I do feel that it would be worth a mention. You may be right in saying that it's more about soil than rock — I don't have much knowledge about that — but my point is that people are going to come here looking for the info, and we should help if we can, even if it's just to say "don't blame the granite, look in this other article". Given that the UK government is blaming the granite, as per the quote above, I think it would be worth discussing. — Johan the Ghost seance 02:35, 9 March 2006 (UTC)
I don't have much knowledge about rocks, soil and radioactivity either - but does this mean that for example kitchen accessories or countertops made of granite are potentionally dangerous? Some of the best and most durable mortars and pestles (popular e.g. in Thailand) are made of granite. I was considering buying one, too, but this radioactivity thing has made me wonder whether food pounded in a granite mortar is "safe" or if it becomes "radioactive", too. I apologize if this is total nonsense...—J. M. 03:31, 21 June 2006 (UTC)
The amount of radioactivity released by a granite countertop is negligible, as is the amount o radon. To reiterate, the radon is only a problem in basements above weathered granites or in soils derived from granite, because the radon gets trapped in the soil, is heavier than air, and is collected within the basement. Your typical kitchen isn't a problem because it is regularly ventilated by windows and the fan in the rangehood(plus, it's only what, 50-100kg of rock?)
A granite mortar and pestle will contribute no measurable radioactivity to any food you grind in it. In fact, I'd say you would have more radioactive elements in the food than the granite bowl.

The average carrot, for instance, would have some potassium-bearing soil attached to its skin, same as a potato, etc. You can get rid of this is you peel it, if you are that concerned. Butpotassium is not a dangerous nucleide anyway, and you will get more exposure from walking out of your house all day to get your daily dose of radiation from the sun while exercising to stave off congestive heart failure.

The way I look it it is that the world is lethal to all life forms. You are going to be killed by something, or a combination of environmental things. This includes radiation. As an organism, you are successful if you get to breed and produce functional offspring before the environment or mishap or predation get you. As a human being, you may believe you can rationally limit the environmental damage received from radiation via any number of vectors, but that may be incidental to whether or not radiation is what kills you. Genetic damage from radiation, such as from UV, is entirely random, hence it is a risk, not a certainty, that cumulative exposure causes problems. There are guys running around who were working in the chernobyl reactor when it went critical, who are now 84 and in perfect health, so...stop worrying about the small things, and worry more about your heart and lung fitness and your driving, eating and sleeping habits or work stress levels. They'll kill you for sure; granite mortars and benchtops may, but no one could ever prove it. Rolinator 09:19, 21 June 2006 (UTC)
If you want to worry about radioactivity, don't worry about a carrot. Worry about your own body. The decay of a carbon-14 atom in DNA happens about 50 times per second, changing a carbon atom to one of nitrogen. (SEWilco 15:20, 21 September 2006 (UTC))

[edit] 200 millirems per year

The text below has been moved to the talk page:

In buildings constructed primarily from natural granite, it is possible to be exposed to approximately 200 mrems per year.[1] .

But 200 millirems is 200 * 1000 / 100 = 2 sieverts per year and 2 sieverts are "the typical background radiation from natural sources, including an average of 0.7 mSv/yr from radon in air". This is close to the minimum dose received by all humans anywhere on Earth" [3]. In other words, while this is true, granite does not add to this. I have removed this from the article as the text seems contradicting itself. Audriusa (talk) 19:21, 7 April 2008 (UTC)

[edit] ORIGIN

Has anyone ever made granite?

Yes. No. Pick one depending on what you mean by that question. Rolinator 03:03, 19 May 2006 (UTC)

Does anyone here know what the hardness of granite is? On Mohs scale of Relative Hardness?

The mohs scale only applies to individual minerals. Not to rocks. But to answer your question, the minerals in typical grtanite are about 6.5 to 7 in hardness. In terms of rock strength the typical granite exceeds 700 Mpa strength. Rolinator

[edit] Chemical Composition

Is it in mol, in mass per cent or something else? 84.160.245.126 15:07, 19 November 2006 (UTC)

Good question, I've just checked the Lakeland Geology reference and it doesn't actually say. I suppose that this info is likely to be in one of the references given in the bibliography section of the book but I don't have easy access to any of them. JMiall 01:20, 20 November 2006 (UTC)
It was wt. % (technically mass percent), but I just replaced the data from a more recent source (1996 vs 1970 whatever) with the number of analyses listed for the average. Vsmith 02:44, 20 November 2006 (UTC)

[edit] alteration of granite

can anybody tell me what is the exact name of the product of alteration of granite, that is a sort of sand including minerals of granite. In french, it's called "arène granitique"

thanks for your help

jacques82.249.96.168 16:42, 31 May 2007 (UTC)

Perhaps you mean grus? No Wikipedia article at present; it is from German for grit or debris and is sometimes spelled gruss. It refers to the "decomposed granite" regolith, the coarse, angular fragments that are the product of (mostly) physical weathering of (usually) granite. Since it is created mostly by physical, not chemical weathering, grus is usually found in arid country. It is not absolutely always applied to granite; I have seen grus that derived from mechanically weathered gabbro. Hope this helps - cheers Geologyguy 18:47, 31 May 2007 (UTC)

thanks for your help. Is grus a commonly used word in english? "Arènes" apart from the "plaza de toros" meaning in french, is quite common in technical french, both geology and pedology/agriculture. It also applies to other rocks than granite, for example gneiss. In France, in Bretagne, Massif Central and Pyrenees, a large part of agricultural soils are grus. thanks again - jacques82.253.17.215 05:17, 1 June 2007 (UTC)

It's certainly common among geologists, and I've known a few non-specialists who use the word, but I would not say it is common in general use. In the US, at least, as mentioned, grus definitely applies to non-granitic rocks as well. Cheers Geologyguy 13:45, 1 June 2007 (UTC)