OK, so to clarify, the 9H is a "pencil hardness" test, not the MOHS scale of hardness that is more commonly used to indicate the hardness of elements and alloys, so to say it's just below Diamonds is not a fair statement. To further clarify, Ghost Glass claims to be "as hard as Steel". In the MOHS scale, Steel, that is - raw steel is only a MOHS hardness of 4-4.5. This is surprising since common Glass starts at a MOHS hardness of 5.5 (with the higher number indicating hardness), and depending on the composition can go to as high as 7 for Soda Lime Glass. By contrast, Talc (think Talcum Powder), is a MOHS hardness of 1, and Diamond (yes, that thing you spent your life's savings on just so she can show it off), is a MOHS of 10 - the hardest natural substance known to man. So I think they mean Hardened Steel (mentioned later)
Now, the Pencil Hardness scale...
- Now, the surface hardness numbers you see for tempered glass screen protectors are based upon the pencil hardness scale, in which the resistance of a coating is determined as the grade of hardest pencil that does not mark the coating when pressed firmly against it at a 45 degree angle. Here’s the complete scale of pencil hardness on the European system that’s most widely used (courtesy of Wikipedia).
- In a simpler term, one would take a pencil, make a line of several centimeters (typically less than an inch), observe if the pencil scratches the surface of the coating, then go down the pencil “grades” until a pencil no longer mars the coating. Surface hardness is defined by the hardest pencil grade that fails to scratch the surface, which is the reason why the procedure is called the “pencil hardness test,” even though it’d be more accurate to call it “surface scratch resistance scale” or “completely misleading title for a scale slash testing. In a very few case where even the 9H pencil unable to abrade the surface, 9H hardness rating designation will be given.
- Source: 9H hardness iloome.wordpress
In the case of 9H, MOST Tempered Glass screen protectors are rated either an 8H or 9H, but that is not the same as a 9 on the MOHS scale. 9 on the MOHS scale is represented most commonly by Sapphire. This is why it's the Holy Grail of screen material. Because it's only able to be scratched by other 9 MOHS substances (such as
corundum,
silicon carbide (carborundum),
tungsten carbide,
titanium carbide,
boron,
boron nitride,
rhenium diboride,
stishovite,
titanium diboride), and by Diamonds, as well as Carbonado (10 MOHS).
So where DOES Tempered Glass fall on the MOHS scale? Well, typically it falls about 7+ on the MOHS scale, which is .5 - 1 below Hardened or Tungsten Steel at 7.5-8. Even the best Tempered Glass screen protectors would only fall in the range of maybe 8 on MOHS, so we could say that 9H on the Pencil Hardness test is somewhat equivalent to 7.5-8 on the MOHS scale, but that is not a fair comparison because the Pencil Hardness test is a SCRATCH test, whereas the MOHS scale is an indication of "Absolute Hardness", meaning throughout the entire depth. Testing MOHS is a combination of scratch and "drop tests". In the case of Tempered Glass, only the SURFACE is resistant to scratches and breakage, but once that surface is abraded, the lower glass is back to the original range on the MOHS scale, and is nearly just as succeptable to breakage as normal Soda Lime glass.
Just a little tidbit for you... Cubic Zirconium (AKA Fake Diamonds) is only an 8 on the MOHS scale, which means it can be scratched by among other things, Tungsten Carbide, so if she owns any Tungsten Carbide (9 no the MOHS scale), drill bits, you might want to rething buying a Cubic Zirconia ring and trying to pass it off as a Diamond...
Here's a great video about Pencil Hardness and it exemplifies what I've described above. By the way, glass cutter wheels are typically made of either Hardened Steel (the lower quality ones), or Tungsten Carbide Steel (the high quality ones), with the latter being 9-9.5 on the MOHS scale, so comparable to and even perhaps harder than Sapphire. I doubt he's using the Tungsten Carbide glass cutter wheel as it would have made mincemeat of that screen protector on even the first swipes.
