Talk:Felsic
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What's going on? Article about acid rock is about something I don't understand and there is a note: "the archaic term for a type of igneous rock, see Felsic". First of all, acid rock is not archaic term, it's still alive and widely used among geologists and it can't be replaced by "Felsic". Felsic is an igneous rock which is defined according to it's mineralogical composition but acidic is an igneous rock witch contains certain amount of silica. So, it's a chemical not mineralogical classification. I hope that it will be fixed. Siim 17:53, 16 September 2005 (UTC)
- As the article says acid rock is an archaic term, that said it is still used by many geologists although it is being phased out by others. The IUGS, Igneous Rocks: A Classification Cambridge 2002, uses it only in the TAS diagram where it simply refers to total silica. The text Petrology by Blatt and Tracy 1996, aavoids using the terminology.
- The terms: acid, intermediate, basic and ultrabasic (corresponding to >65%, 52 - 63%, 45 - 52%, and <45% SiO2 on the current TAS) were introduced to petrology in the 1800s referring to silicic acid - this is no longer the meaning and the terms have no relation to pH or acidity in the chemical sense and therefore are misleading and, in my view, should be avoided. Even though the terminology is archaic and misleading, it is still used by some geologists so needs to be defined better here, but used only sparingly. The terms: silica saturated, unsaturated, and supersaturated are perhaps more meaningful, although also confusing perhaps. Why not just high silica, intermediate silica and low silica or give the percent silica instead? Vsmith 02:09, 17 September 2005 (UTC)
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- I know that all what you said, but it won't change my point. Main problem is that wikipedia says acid rock is archaic term, see Felsic. It creates impression that term "acid rock" is no longer used and it is replaced by "felsic rock" but both statements are wrong. Acid rock may be archaic in most cases but it is still used in TAS diagram and TAS diagram is far from being archaic. It is archaic mainly because lots of geologists think erraneously that acidic and felsic are synonyms. I agree that terms acidic and basic are no longer used as widely as they were used in the past but I don't like if wikipedia oversimplifies these things. We don't need long article about acid rock, even short stub would be helpful. Siim 09:23, 17 September 2005 (UTC)
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- OK. I did some modifying of felsic, Igneous rocks, and Acid rock to hopefully clarify a bit. More needed including perhaps an article on the acid - basic - ultrabasic usage in petrology, both historical and current - maybe someday :-) Vsmith 17:04, 17 September 2005 (UTC)
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[edit] Contradicton
At the begining of the article, Hornblende is one of the felsic minerals in the list. In the section "Classification of felsic rocks" it's a mafic mineral. Which one is correct? Avihu 11:01, 20 January 2007 (UTC)
- Hornblende is mafic mineral. Siim 11:36, 20 January 2007 (UTC)
