How much does diamond dust weigh?

[buzzard]

Hi all! Interesting Thread.



I don't mean to hijack the thread but has anyone ever considered the hardness modifier between deformable (eg. metal) and non-deformable (eg. stone/gemstone) materials.

I mean based on pure hardness alone glass is actually tougher than iron (yet has one tenth its hardness in the PHB). Diamond is between 16-32* times tougher than iron (lets take the average of 24 for simplicity sake). So this would constitute a Hardness rating of 24 if we applied the same relationship between glass and iron (1/10th).

*Depending on certain variables.

However, the 'black sheep' of the family is of course Stone which is given as Hardness 8.

If we were to base Diamond on the Stone-Iron relationship it would be Hardness 240.

So is Stone wrong or is Glass wrong? (Personally I think the former)

Any Comments?

<whips out metallurgist hat>

OK the problem here is that D&D uses a bad term. It seems logical enough that hardness would work to describe how "hard" something is to break, but it doesn't. It causes complications based on real work hardness meaurements.

In the real world hardness is measured by how much force is required to locally deform a substance . Usually this is done using an indentor. It is directly indicative of the strength of the interatomic bonds in the substance (be they metallic, covalent, or ionic).

However this does not tell you anything about how much energy it will take to break the material. When you break something you, in almost all cases, induce fracture. Thus the key to how tough (which means how much energy is needed to break) a substance is, can be related to how hard it is to propagate a crack through it.

Metals are generally quite tough. They are tough because they are malleable. Stone, diamonds, and glass are not tough because (at room temperature) they are not at all malleable. This has to do with the nature of the bonds, and the atomic stacking.

What does malleability have to do with cracks? Well, a crack works by concentrating stress at the crack tip. Because of this concentration, a mild load is able to break very strong bonds, because it is only doing it to a few bonds at a time. In the case of a malleable material, a region around the crack tip deforms, which distributes the stress, thus blunting the crack tip.

Unknown to most people it is possible to make ceramics which can be tough. You just do it by playing some complicated games (too complicated to explain here). I have played with a ceramic hammer before. However this technology is certainly too modern for a D&D setting.

But, to get back to game mechanics, the value for glass is probably fine. Glass has an amorphous structure which, at room temperature, is incapable of rapid deformation because there is no way for atomic stacks to slide past each other in a uniform manner (which is about as simply as I can put it without explaining dislocation theory).

I definitely don't recommend upping the hardness for diamonds. They are, like glass, extremely brittle. If you happen to be a De Beers heir, you can test this out by hitting one with a hammer. It will shatter.

Also, please don't starting thinking about tensile strength. It is generally not a useful measure for about any practical purpose. Yield strength is generally accepted as much more useful, though in this case it still isn't a good bet. If you take a small enough glass fiber, which has no cracks, it will have an enourmous tensile strength. Diamond would be even stronger by this measure. However both of these materials have poor toughness, which is what you should care about.

If you want a tough material it has to be both strong and malleable. This pretty much limits you to metals (and composites, but D&D doesn't tend to have those).

buzzard

 

[Umbran]

I'm inclined to think "diamond" should just be taken as "hard precious stone." We're talking quasi-medieval culture, and pre-modern notions of mineralogy were extremely vague.

Yes, but the game waws written by modern folks, with modern ideas of what gemstones were, and without much attention to the details of historical niceties. When the rulebook says "diamond", I'm sure the author's intent was what the player will think of as "diamond", rather than what a 11th century philosopher would think of as "diamond".

 

[isoChron]

If you take all hard precious stones as diamonds then there wouldn't be any quartz, ruby, sapphire, emerald, or whatever gemstone you can think of.
True gemstones are alltogether very hard (Mohs>=7), which is the determining factor for true gemstones.

The specific weight of diamond is 3.5 g/cm^3. That means that a cube with edges of 1cm lenght only weighs 3.5g (17.5 carat).
An average diamond is worth 5000gp (FRCS p.300). A diamond of 1 carat would for sure be more than average but lets take it for average. That means that 0.2 gramms of diamond are worth 5000gp. That's a pinch. Now talk about 1/50th of that. Even if you carry diamond dust for 87500 gp (17.5 carat) with you it would be hardly more than a cubic inch (because it's dusted instead of one solid crystal) and weighs 3.5 gramms.
The container to carry the dust safely weighs more than the dust itself even if you use folded paper.

For the hardness I can only second buzzard. All said.

BYE

 

[Voadam]

Have a couple of ideas from my e-book, the Enchiridion of Mystic Music:




--The Sigil

Those are in your bard book and not the treasure one?

 

[The Sigil]

Those are in your bard book and not the treasure one?

D'OH!
You're right. They're in the Enchiridion of Treasures and Objects d'Art.

Been a long couple of days around here.

I'll go change the parent post.

--The Sigil

 

[tarchon]

Yes, but the game waws written by modern folks, with modern ideas of what gemstones were, and without much attention to the details of historical niceties. When the rulebook says "diamond", I'm sure the author's intent was what the player will think of as "diamond", rather than what a 11th century philosopher would think of as "diamond".

Well duh. I know the author's intent was what we call diamond, but if you want to think of the game setting as being more than a set of arbitrary rules, it probably makes more sense for the spell component in a medieval milieu to be hard precious stone, probably known by some local name that may or may not be what people call it in other areas. I doubt more than 5% of the people reading this group can tell a piece of quartz from a diamond even with a modern education, and the idea that you can just run down to the store, buy a "diamond," and know for sure what you're getting is more consistent with steampunk than medieval fantasy, unless there's a spell called <i>Identify Rock According to a Classification Scheme That Hasn't Been Discovered Yet</i>.

 

[mythusmage]

<whips out metallurgist hat>

OK the problem here is that D&D uses a bad term.(snip)

The term I've heard used for toughness is 'shear strength'. This along with 'shear modulus' and density are what determines how tough an object is. The higher the shear strength, shear modulus, and density are, the tougher the material.

Crystals tend to have a lower shear strength and modulus for their density. So do entirely amorphous objects. It's the partially amorphous, partially crystalline objects (such as metals) that do the best.

The toughest metal I've run across is an alloy of palladium and iridium. But, it's also very heavy, and incredibly expensive. After that you get into the steels. But the really tough steels are the product of modern day metallurgy. In a medieval setting you're more likely to find mild steels, and many of those are actually weaker than standard bronze.

Then you have wrought iron, which has its uses, but you really shouldn't use it in battle.

Probably the toughest affordable metal is cast iron. But that requires a level of technology the typical D&D world won't have. Especially white iron, which requires a carefully controlled drawn-out cooling down period to produce. In addition, it's the wrong type of tough. That is, cast iron can take a lot of pressure applied for a long period of time, but a 'short, sharp, shock' will crack it like nobody's business.

(I'm rambling. I will now stop it.)

As to diamond dust. You don't need to bust up a rock to get any. Find somebody who specializes in cutting diamonds and ask him if he has any dust for sale. He should.

The initial steps in producing a gem quality diamond produces lots of dust. As can he later stages. In addition, most diamonds are not gem quality. These industrial diamonds are often broken up for abrasives. A diamond cutter of gem dealer may have so much diamond dust around he'll pay you to haul it away. By this measure your character may have to buy as much as a hundred pounds of diamond dust to get the amount needed.

But, It's more likely what needed is gem quality diamond dust, which you can only get by powdering a gem quality stone. The question now arises, how high in quality must the stone be?

A perfect stone of the same weight will go for a higher price than a flawed stone. One that barely qualifies as a gem stone is going to be real cheap. At the same time color will inpact value, and that will depend on current tastes in diamonds. (I can remember a time when yellow diamonds were cheap where diamonds are concerned, but now a canary diamond (same color, different name) demand a premium price.) Then you have the matter of 'inclusions'. Imperfections that form a pattern. A star sapphire, for instance, can command a higher price than a perfect diamond of the same weight.

(The Pink Panther Diamond of the movie series is a fictional example of a flawed stone with a higher value because of the 'pattern' of the flaw.)

For the amount most PCs are apt to purchase a beeswax sealed envelope of smallish size will suffice to hold it. Probably about an inch on the side would work best. But, the dust in question will most likely sit in one corner looking rather lost.

In which case, don't bother trying to 'fish out' the dust. Instead your PC should open the envelope, invert it, and let the dust fall out as he chants the incantation. He can then use the now empty envelope as a fire starter.

Hope this made sense, sometimes my mind wanders.