Monday, November 8, 2021

Mohs Scale to Marvel

Mohs scale hardness testing kit

Regular readers of this blog may know how much I adore finding some real-world measurement scale that can be easily used as the core of a game system mechanic. If available, this ticks off all my desired boxes for gaming: (1) an elegant mechanic, (2) a presumably rigorous mechanic, (3) an opportunity to learn something about the real world, and (4) provide a pre-made way to convert from real-world data to the game. 

Of course, if we look back to the origin of the wargame form, the entire intent was to use real-world data as a source for mechanics and training for the battlefield (say, at least as far back as Korns' Modern War in Miniature, if not original Kriegsspiel). So, this instinct is really a callback to our source inspiration. 

Here's the thing I just discovered: the Mohs scale of mineral hardness. This dates to 1822 when German geologist Fredrich Mohs established the system to measure relative hardness -- a mineral of higher-rank is able to visibly scratch the surface of a lower-rank material. (Per Wikipedia: "The method of comparing hardness by observing which minerals can scratch others is of great antiquity, having been mentioned by Theophrastus in his treatise On Stones, c. 300 BC, followed by Pliny the Elder in his Naturalis Historia, c.  AD 77.")

It's an incredibly simple system: integer values only, from 1 to 10 -- with talc at the lowest level, and diamond at the highest. Note the picture at the top of a standard field-testing kit, with the 10 different canonical materials neatly boxed and numbered. 

Also I realized, if you're a fan of the the original Marvel Super Heroes RPG, this neatly lines up with the 10 named ranks in the Universal Table. To wit:

Mohs Scale to Marvel Table
As usual, the neat thing is that having established this, there are now extensive tables of other materials with hardnesses measured in possibly fractional Mohs units; so for these other materials we have the option of just looking them up and converting to the nearest rank value. Example from Wikipedia below (click to go to full-sized table).

Intermediate Hardness Table

A number of these substance appear in the MSH rulebooks Material Strength table (like ice, gold, glass, iron steel, and diamond), and in most cases they do in fact appear at the same or within one rank. So kudos to Jeff Grubb for a pretty accurate system on that score; and that gives us confidence that we can interpolate these things reasonably in-game.

It's science, true believers!


  1. Excellent. As a geologist, this post receives my rock hammer of approval.

  2. The Official Handbook of the Marvel Universe (in its original version anyway) gave Mohs hardness ratings for some characters' skin. I remember that they rated Wonder Man and Luke Cage, and no doubt others.