Talk:Mohs scale of mineral hardness
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- 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).
- 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
- 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.
- 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.
Question: What is the absolute hardness of moissanite?
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)