Talk:Mohs scale

message: :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 the 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 feldspar, and a small percentage of a mafic mineral (generally biotite or hornblende) 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)
thread_title:  Linear scale 

message: 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)
thread_title:  Absolute hardness of moissanite? 

message: 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)
thread_title:  Why is "liquid" listed on the second/extended table? 

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

message: 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)
replies: text: 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)
thread_title:  Window glass 

message: 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)
replies: text: He must have confused it with the Ridgeway scale, which modified by Moh's by putting diamond at 15 J1812 (talk) 11:52, 17 December 2014 (UTC)
thread_title:  Mohs Scale 

message: with the mohs scale table, can we add carbonado about it has the same strength as diamond and is a fairly notable example of a mohs 10 that few people have heard of. : D please add. Tincanmansiimon (talk) 19:09, 12 September 2012 (UTC)
thread_title:  Carbonado 

message: 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)
thread_title:  Diamond not readily available? 

message: Newly occurring materials harder than diamonds have been recently discovered. It is unclear how this will affect Mohr's scale. At the very least some wording will need to be changed on this page to incorporate this; ie: "As the hardest known naturally occurring substance, diamond is at the top of the scale." I am not sure how mentioning the new materials should be handled and I can't find anything on how it might affect Mohr's scale (I would guess the materials would be assigned a number above 10 rather than renormalization). 
Link to story: http://www.newscientist.com/article/dn16610-diamond-no-longer-natures-hardest-material.html
User:Nicf 08:26, 18 February 2009 (UTC)
replies: text: For further reading, you may also find the following page of use: http://www.itvnews.tv/Sci-Tech/Science/diamond-is-no-longer-natures-hardest-material.html
79.71.190.207 (talk) 00:12, 20 February 2009 (UTC)
thread_title:  Natural occurring materials harder than diamond affecting Mohr's Scale 

message: Delete reference to the article of Zarechnaya et al. These people were not the first ones to measure the hardness of boron. Weintraub was the first one to give qualitative (9.5 by Mohs scale) measurement, Solozhenko et al. were the first to give quantitative measure (50 GPa).
I see that user Materialscientist has persistently reverted deletion of the the reference to Zarechnaya et al. I also see that on WP this user has generally created a lot of references to these people (group of N.Dubrovinskaia). I am aware that Materialscientist is a collaborator of N.Dubrovinskaia, and this should make him ineligible to promote her worksNo more D (talk) 19:42, 11 September 2010 (UTC)
replies: text: None of the instances talks about priority, thus your concerns do not apply, but your personal attacks are not appreciated. Materialscientist (talk) 23:28, 11 September 2010 (UTC)

text: That someone is someone's friend, and that something was proven incorrect are mere speculations. Your are banned user Aoganov, who came to wikipedia with a single purpose to promote your work, and discredit anyone who stands on your way, by any means possible. I got involved in this whole issue only because someone from Dubrovinskaia group contacted me on my talk. I was first skeptic to all parties for quite some time, and then you showed what you're up to. Cease and desist. Those references (yours and of Dubrovinskaia) stand here because of WP:NPOV, to present both sides of research. Materialscientist (talk) 11:23, 10 July 2011 (UTC)
thread_title:  Hardness of  boron 

message: Under the table, the text says that a steel file has a hardness of 6.5 and a streak plate has a hardness of 7. Neither of the two footnoted links in that section give a hardness for a "steel file". One gives a "steel nail" as 5.5, and the other gives a "steel needle" as 6.5. They give different hardnesses for a streak plate, 6.5 vs. 7. The subsequent intermediate hardness table lists steel as 4 to 4.5, and hardened steel as 7.5 to 8.NoJoy (talk) 17:34, 12 October 2010 (UTC)
thread_title:  Inconsistencies 

message: I have removed a statement 
:Since the invention of the Mohs scale of mineral hardness, there have been reports of materials harder than the highest mineral on the scale, diamond; so the Mohs scale may be changed in the future.
Per WP:OR - neither it is present in the cited reference nor there is any reliable experimental report of material harder than diamond. Materialscientist (talk) 01:07, 15 March 2011 (UTC)
replies: text: Look at the links in the comments above. You are wrong.  — Preceding unsigned comment added by 175.180.196.236 (talk) 09:49, 7 June 2011 (UTC)
replies: text: There are two types of reports on materials "harder than diamond". One is experimental work on ADNR, which is diamond, but in a nanocrystalline form. Another is theoretical, on lonsdaleite - needs to be confirmed by experiment, which showed that lonsdaleite produced so far is too defective and has a hardness significantly lower than diamond. Materialscientist (talk) 10:06, 7 June 2011 (UTC)
thread_title: [[WP:OR]] removed

message: On the same wikipedia page, elemental chromium is stated as having a hardness of 8.5 on Moh's scale and then in the last chart it is written 9. Chromium is absolutely NOT as hard as corundum, since Moh's scale is not a proportional scale, and with around 1GPa Vickers hardness, chromium doesn't compare well with alumina, in other words, there is a substantial difference between 8.5 and 9 in Moh's scale. Mindat.org is NOT a reliable source, there are loads of inconsistencies and inaccuracies on that site, why is it referred to so often on wikipedia?  — Preceding unsigned comment added by 82.240.163.245 (talk) 22:54, 5 February 2012 (UTC)
replies: text: Thanks, I have lowered 9 to 8.5. There is an intrinsic problem with metals that their hardness can vary several times or more depending on the history (thermal and mechanical) of preprocessing. Materialscientist (talk) 02:01, 6 February 2012 (UTC)
thread_title:  Hardness of chromium 

message: There is a mnemonic for remembering the Mohs scale. Can't remember it (oh, the irony..). Shouldn't that have a mention? VenomousConcept (talk) 13:47, 2 March 2012 (UTC)
replies: text: Looked it up, the mnemonic is : Toronto Girls Can Flirt And Other Queer Things Can Do VenomousConcept (talk) 14:56, 2 March 2012 (UTC)
thread_title:  Mnemonic 

message: Error! stishovite is harder than tantalum carbide(<9.5), invert them in table!  — Preceding unsigned comment added by 84.221.100.6 (talk) 13:57, 12 May 2012 (UTC)
replies: text: References please --Chris.urs-o (talk) 14:23, 12 May 2012 (UTC)

text: I updated the stishovite and this article. Mohs scale is very approximate, and there is much spread in stishovite hardness (anisotropy, sample dependence - stishovite samples are relatively rare), thus it is often uncertain which material is harder. Materialscientist (talk) 10:09, 13 May 2012 (UTC)
thread_title:  Carbide 

message: Titanium diboride and stishovite are at wrong position in table: with their ~30 GPa Vickers they should be lowered 
to 9-9.5, not 9.5-10 (at least ~40Gpa) wherein B6O and ReB2 could be placed.
78.12.118.38 (talk) 22:01, 24 May 2012 (UTC)
replies: text: Values vary from report to report, and 30 or 40 is quite the same for the Mohs scale. Some reshuffling might be needed, but better one. Materialscientist (talk) 22:31, 24 May 2012 (UTC)
thread_title:  Edit request on 24 May 2012 

message: Early on, it explains that Mohs scale is an ordinal scale.  In the table that follows, we see that the absolute hardness values are irregular with respect to the Mohs values.  This seems to be saying that only the integer values from 1 to 10 inclusive are defined, and no substance can be said to have a particular Mohs value outside this set – it can just be said to be "between 5 and 6" or "below 1", for instance.
And yet immediately below the table, and in the section that follows, specific non-integer values are given for a number of materials.  Does this mean that Mohs added these intermediate points to the scale since originally publishing it?  Or that somebody has invented a formula (maybe a piecewise linear, or piecewise exponential, or cubic spline, or just a 9th degree polynomial) whereby the sclerometer output for a given material can be converted into a Mohs value?  If the article is going to mention specific intermediate values at all, it should at least explain them. — Smjg (talk) 18:37, 16 February 2014 (UTC)
replies: text: I'm also curious about this, and unfortunately it doesn't look like there have been any updates in the last 6 years.  Some googling indicates that in some contexts, 5.5 just means "between 5 and 6", but I've also seen vague references to more specific extensions of the scale.  (Such as this google book result about lignites.)  Ideally someone with specific knowledge could add a note to the page about this?  --71.163.110.245 (talk) 18:16, 16 February 2020 (UTC)
thread_title:  How are intermediate values determined? 

message: Maybe there should be a note of this. For example, a steel axe is much harder than any wood, but this doesn't mean that your steel axe will never wear out chopping trees/wood. Nor does it mean if have a tongue ring that you can't scratch the enamel off your teeth with it with repeated rubbing. There's more to it than hardness, what about the amount of force used. A spinning steel blade circular saw could cut a tooth couldn't it- even if the tooth is a higher hardness. The snare (talk) 02:10, 17 March 2016 (UTC)
thread_title: Doesn't mean a lower hardness scale material can't effect a higher one

message: 208.108.212.76 (talk) 13:21, 28 January 2016 (UTC)
replies: text: - that is what the article states - Arjayay (talk) 14:51, 28 January 2016 (UTC)
thread_title:  Semi-protected edit request on 28 January 2016 

message: Is there a reason why the article does not use the definite article, or is that an omission?  I.e., is there a reason to say "Mohs scale of mineral hardness is…" instead of "The Mohs scale of mineral hardness is…" ? –Jérôme (talk) 11:23, 13 November 2016 (UTC)
replies: text: You're talking about the lead sentence? I agree, it sounds awkward. The rest of the article uses "the" in front of "Mohs". I'll go fix that sentence. — Gorthian (talk) 00:10, 14 November 2016 (UTC)
thread_title:  The Mohs Scale 

message: Now that there are expectations that Lonsdaleite manufactured/fabricated in a lab will be harder than diamond, when will we be able to add it to the scale/list/table?
77.126.20.27 (talk) 23:30, 13 December 2016 (UTC)
thread_title:  Man made Lonsdaleite 

message: In the table giving the chemical formulae of the minerals making up the scale, for talc we have "(OH)2", but for apatite "(OH-,Cl-,F-)", and topaz "(OH-,F-)2". In the Wikipedia entries for apatite and topaz, the article doesn't give the "-" indicating the ionic charge, as we don't for talc in this article. Is there any reason for the inconsistency? Peace Makes Plenty (talk) 16:28, 23 February 2017 (UTC)
thread_title:  Specifying some formulae as 'OH<sup>-</sup>' and others as just 'OH' 

message: Hello fellow Wikipedians,
I have just modified one external link on Mohs scale of mineral hardness. Please take a moment to review my edit. If you have any questions, or need the bot to ignore the links, or the page altogether, please visit this simple FaQ for additional information. I made the following changes:
*Added archive https://web.archive.org/web/20081017152845/http://www.inlandlapidary.com/user_area/hardness.asp to http://www.inlandlapidary.com/user_area/hardness.asp
When you have finished reviewing my changes, you may follow the instructions on the template below to fix any issues with the URLs.
Cheers.—InternetArchiveBot (Report bug) 19:58, 21 January 2018 (UTC)
thread_title:  External links modified (January 2018) 

message: Why is this listed in two different places on the intermediate scale? Jokem (talk) 03:10, 6 April 2021 (UTC)
thread_title:  tantalum carbide 

message: Why is the Mohs scale being compared with the Vickers scale in the article? Aren't they measures of two different qualitiesrespectively, scratch hardness and indentation hardness? Largoplazo (talk) 22:32, 15 October 2022 (UTC)
thread_title:  Comparison with Vickers