Talk:Mohs scale of mineral hardness

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[edit] Linear scale

Question: if the scale isn't linear is there a linear scale that geologists prefer to use? And what exactly is 'absolute hardness'? How is hardness defined (we know what it is intuitively, but what is its physical definition?) Are there SI units for hardness? -- SJK
There is no absolute hardness scale. No units for hardness either. As for what "hardness" really is, I think that is an open question. It would certainly be related to fracture toughness, but that defies analysis as well, relying on laboratory testing and depending on the geometry of the specimen.
A simple search on Google shows there is an 'absolute hardness' scale; in fact, there appear to be at least two: the Rosiwal absolute hardness scale; and the Knoop absolute hardness scale. Also, how can a non-existent scale yield real numbers like the ones in this article (although I've more commonly seen 140000 for Diamond, not the 1500 given above; I suppose this might be the Rosiwal vs. Knoop scales.) -- SJK
What defines hardness depends on the scale you use. The Rosiwal scale measures resistance to abrasion and uses an arbitrary value of 1000 as the hardness of corundum as its basis (diamond comes out to 140,000). The Knoop scale measures how deep a standard diamond pointed tool can cut into a material given a standard amount of pressure pressure (diamond comes out to 7000 in this scale).
Isn't part of the definition of hardness the scratch test (if you can scratch something with something else, that something else is the harder of the two)?
Thats the point of the Mohs scale. Frankly, the most useful materials for hardness testing in the field are fingernails (hardness 2-3) and pocket knives (hardness 5-6). Used in conjunction with luster, crystal habit and color, fingernails and pocket knives do a pretty good job.

The real answer to all this discussion (just above is part of it, too), is that Mohs scale is a field test, really. All of the things on the scale are minerals - "pure". In the field, one picks up a rock and scratches it. Granite is a great example because it contains quartz, orthoclase and feldspar all in one. Even if there were an "absolute hardness", it would be no better, because rocks are not "absolute". There are many variables in rocks, grain structure, grain orientation, inclusions, mixtures - all sorts of stuff. If you have a "Jade Sculpture" and you can scratch it with a knife, it's not jade, it's something else. That's it's use - just one clue as to identifying a rock or mineral. That doesn't make Mohs scale trivial - probably 100% of amateur and pro geologists and minerologists in the world know and use it. Jjdon (talk) 21:35, 2 February 2008 (UTC)

[edit] Absolute hardness of moissanite?

Question: What is the absolute hardness of moissanite? Answer: Moissanite is crystalline silicon carbide, also known as Carborundum, which is on the scale below. The absolute hardness I for one don't know. Jjdon (talk) 20:33, 30 January 2008 (UTC)

[edit] Why is "liquid" listed on the second/extended table?

Question: why is "liquid" listed on the second/extended table? It's been there since the table was created, and I cannot see why it isn't "Talc" there. 194.106.59.2 15:27, 23 Apr 2005 (UTC)

[edit] Nationality of Friedrich Mohs?

MANY SOURCES say that Mohs was Austrian, Many say he was German - The article does not make this clear. I know that he worked and lived mostly in Austria, but this neither makes him Austrian or German by default. His nationality should be clarified.

[edit] Absolute hardness?

Maybe someone could link to the appropriate article, or write it if it doesn't exist.--345Kai 09:23, 4 December 2006 (UTC)

[edit] Nobody has noticed, but 81.153.226.47 keeps adding penis to this article

Nobody has noticed, but 81.153.226.47 keeps adding penis to this article

Maybe, but there's no question about the fact that the discussion of minerals makes him very hard.

kind of related: "Moh's Hardness Scale Mnemonic: The Gay Cowboys Frolicked Around Peaks Quietly To Cease Depravity" anyone have a clue what Peaks is supposed to be for?

Talc Gypsum Calcite Fluorite Apatite Platinum? Quartz Topaz Corundum Diamond

Plagioclase ? (covers a fair range of compositions and hardnesses I know, but mnemonicists don't normally care too much about the details. My DH&Z gives plagioclases as 6-6½.)
A Karley (talk) 05:35, 16 April 2008 (UTC)

[edit] Window glass

I think window glass is somewhere near quartz, since the two are very similar in composition. Thus I have changed it to 6.5 unsigned

Very scientific.68.145.207.92 03:03, 11 January 2007 (UTC)
Must be right. I think graphite and diamond must be pretty similar as well. I mean, it's basically the same thing. Dept of Alchemy 21:08, 20 February 2007 (UTC)

[edit] Mohs Scale

Diamond is 10 on Mohs scale. For some reason diamond showed up as 15 on the table, so I changed that. Dept of Alchemy 21:10, 20 February 2007 (UTC)

[edit] Diamond not readily available?

I removed the paranthetical diamonds exception from "All readily available (except diamonds)" Diamonds are certainly readily available--you can get them at hardware stores all over the world! And they are by no means a rare mineral. (the reasons why they are so high-priced isn't because they are rare.) As a matter of fact, if you were challenged to find flourite or diamond in a limited amount of time, for prize money, unless you happen to live near a university with a geology department you'd probably be better off choosing to search for a diamond. Brentt 22:33, 23 February 2007 (UTC)

I take your point, but fluorite isn't exactly hard to find either. It's moderately popular in jewellery. Look for "Blue John". A Karley (talk) 05:24, 16 April 2008 (UTC)