# Would steel armor with gems embedded within its design be weaker than regular steel armor?

The gem in question is emerald. The design has a large emerald in the center of the chest, and emerald on the shoulders, knees, and elbows. Would the emeralds be weak points in the armor? Would the design make any practical sense at all?

Note: The reasoning behind the emerald in the armor is spiritual.

• Are these magic gems? – Wayne Werner Jul 7 '16 at 14:24
• @Wayne Werner they're emeralds. Are emeralds magical? – Aarthew III Jul 7 '16 at 15:48
• @AarthewIII I don't know - this wasn't tagged hard science, and the OP said that the reason behind the emerald in the armor is spiritual. It's entirely possible that there's a handwavy magic component to them. – Wayne Werner Jul 7 '16 at 15:53
• Emeralds shatter quite easily. I don't think that's a feature you want in your armor. – Joe Jul 7 '16 at 17:59
• @WayneWerner It's merely symbolic for the military. No magic. Although, I could easily change that. – autumnstorm451 Jul 7 '16 at 22:20

## Yes

Any change in material or join is a weak point or a stress point.

If the gem was an integral part of the armour then the gem would be a weak point:

1. because the join is a weak point

2. because the toughness of the gem differs from the metal and it would flex differently passing more stress to the join

3. risk of the gem shattering, gemstones are hard, hardness is a measure of resistance to plastic deformation, where the tougher metal will flex and eventually permanently bend to absorb energy, the gem, once it passes the equivalent higher threshold, will shatter. Repeated impacts which would leave metal armour battered and bent will leave a big hole where your gem used to be.

If the gem was overlaid onto the the armour (with full continued armour behind) as decoration then only 2. applies.

• If the gem is integral to the armour, wouldn't that result in glass shrapnel going into the wearer? – Philip Rowlands Jul 7 '16 at 13:35
• @PhilipRowlands, only if the gem shattered, they're very hard and I wouldn't expect the gem itself to be a point of failure. The preferential point of failure would be the join, once the join has failed there's no longer stress on the gem. – Separatrix Jul 7 '16 at 13:36
• @Separatrix Hardness does not imply strength; only resistance to scratching. You can shatter diamond with a hammer. – Schilcote Jul 7 '16 at 21:55
• @Schilcote As you say, hardness is not strength, however hardness does imply transfer of stress for stresses below breaking point. – Separatrix Jul 8 '16 at 5:42
• What about chain mail armour? – Victor Stafusa Jul 10 '16 at 17:42

You don't have to weaken armor to decorate it.

First, gems are never going to make plate or other metal armors better at their job.

• Plate armor is best when it has as few joints, beyond what is necessary for mobility, as possible.
• Never make the gems relevant to plate armor's structure. If you must have them they can simply be added to the exterior of the armor. This way they would have no negative impact on the structure of the steel.
• Connecting anything to mail armors is going to be difficult.
• Scale armor could be a good choice as you could stud the scales with stones if you want...that'd be shiny and make you look like a dragon... cool idea noted

Non metal armors on the other hand could potentially benefit. Gems are hard...studded leather made from gems could potentially be useful.

Negatives of using gems in armor

• Makes the wearer a target. Many in ancient combat were there for the loot...emerald studded armor would probably end badly
• Definitely agree with this one. As long as your emerald was set in a bezel that was stuck to the surface of otherwise normal armor, then it would not compromise the armor. You essentially want to bedazzle your armor, not embed the gemstones into the actual structure of the armor. – guildsbounty Jul 7 '16 at 13:51
• I rarely disagree with you but I must here. Any change to the surface of the armour would weaken it. Even soldering on simple gem mounts to the outer surface would create stress points around them. That wouldn't necessarily be significant of itself but once you add the gem it creates an area that wouldn't flex in quite the same way on impact amplifying the effect. – Separatrix Jul 7 '16 at 13:53
• @Separatrix Medieval armor was not made of the thin sheet steel we have today. So while yes, it is technically true that even soldering creates stress in the steel it would be minimal. Flex would be irrelevant as the gem is not structurally part of the armor. The steel behind would function exactly the same as the steel around it. – James Jul 7 '16 at 14:07
• @Separatrix I think the question of whether or not it would weaken the armor meaningfully is a question of how the mounting is designed. I think you should be able to find a mounting which has the correct damping behavior to have less of an effect on the armor than, say, the armorsmith sneezing at an inopportune moment while crafting it. – Cort Ammon Jul 7 '16 at 14:30
• As an example, I've given you cloth armour and a slightly domed (so it doesn't just fold up) circular breastplate. I then hit you smack in the centre of that breastplate with an enormous hammer. You're going to have a circular bruise, that bruise represents the increased stress at the edge of the gem. No matter where on that breastplate I hit you, the impact on you is on that circle. As it's on cloth it represents @CortAmmon's damped connection, this means that impacts elsewhere outside the breastplate don't affect that stressed boundary the way they would on a harder medium. – Separatrix Jul 7 '16 at 16:26

Armor are greatly underrated in fiction. A man in full plate armor is close to a walking tank. To defeat him you will aim to the gap in the armor.

If you're rich enough to incorporate large emerald in your armor, the armor is probably well made enough that it can take a warhammer hit, it will not be perforated. I'll take a recent example in Game of Thrones, The Mountains took a warhammer strike from one of those religious fanatics. It results holes in the armor. That is not realistic. Thats not armor steel. That is cheap thin aluminium. To penetrate heavy armor you need heavy crossbow and a good angle, or a spear and a horse at full speed.

As others said before, yes it will weaken the armor but does it will make a difference ? I think not. If you don't heavily change the structure of the armor to incorporate the gem and if the gem is on the outside of the armor it will not be a problem.

Of course a powerfull hit can unseal and/or break the gem.

• As a followup on how much of a walking tank they are, other commenters would be advised to watch reenactors doing full-force combat sessions with axes and warhammers. There's usually significant visible damage to the armour, but rarely to the person inside it. – Graham Jul 7 '16 at 16:31
• Exactly - while the other answers focus on the theoretical weakening of the armor, you should ask yourself: When wearing full plate armor in a medieval setting, what attacks will bring enough stress to even come close to breaking this armor??? Almost none, so even if the gem would weaken it, it wouldn't matter. Piercing Crossbows would still pierce it, everything else would still bounce of 99% of the time. – Falco Jul 8 '16 at 12:30

Someone rich enough to have a plate-sized emerald on the chest of their ceremonial armor has no place on the front line anyhow. Usually, such armor is the domain of kings, who would not wander onto the battlefield without a guard of hundreds surrounding them on all sides. The role of the person such in ceremonial armor on the battlefield is two-fold:

1. Act as a HIGHLY VISIBLE morale-boosting mascot, i.e. get the promotion-seeking officers thinking "The King is watching us, let's show him what we can do."

2. Use part of his own Elite Guard to reinforce critical points in the front line, that seem likely to buckle under enemy pressure or where a rapid-reaction force can exploit a weakness.

To answer the question, by definition a gem-studded armor will be weaker than a smooth, blow-deflecting purely utilitarian full plate. Gems are hard, yes, but they can often also be brittle. The extra weight of the stones and the setting can hamper movement. Normally, this sort of potentially-lethal extravagance would be only used as ceremonial plate, only worn during parades to impress the ladies and the plebs.

• The Black Prince's "Ruby" (that big ole' red jewel on the Imperial crown) was worn by several royals on their battle armor. – Kys Jul 7 '16 at 15:11
• Do it for the ladies...true. But what about the lady warriors...they deserve to see the bling too. :) – James Jul 7 '16 at 15:20
• @Kys, given that said royals wore it in their helmets and died (or nearly died) on the battlefield due to ... headblows, it hardly seems like an endorsement. – Serban Tanasa Jul 7 '16 at 19:41

Would the emeralds be weak points in the armor?

Yes.

The emeralds are either integral to the armor (i.e., there is emerald somewhere there should be steel) or they are not (i.e. they are attached to the surface somehow: clasps, claws or clasping bands).

If they are integral to the armor they represent weak points, where the armor may either break or be penetrated. Gems, while hard, are often brittle and can be shattered by a strong enough blow.

In both cases, you want an armor to be smooth and rounded, without dents, inflections or hard edges that could give purchase to a blade or point (e.g. the beak of a halberd) to either transfer shock to the wearer, or even worse penetrate it. In certain circumstances, any decoration on the armor can act like a guide, turning an incoming arrow or bullet in instead of deflecting it away.

If the gem is only encrusted upon the steel as ornament, it will just be dead weight. But such gems are pretty light, compared to steel. Some quick googling has the density for emeralds at around 2.76 grams/cm3. Steel, on the other hand, is around 7.8 grams/cm3. For comparison, the density of water is 1 gram/cm3.

Now, the emeralds may protect you metaphisically - I won't argue about that, you world, your rules - but if you intend for them to protect someone mechanically, your knights are in trouble.

A lot of people are going to tell you that emeralds and diamonds are awesome because they are hard. But that DOES NOT make for armor material.

Armor protects you in two ways. It either deflects blows, or absorbs impact for you.

Now, I don't see your emerald deflecting a mace, for example. It won't have the shape for it. So let's try absortion.

Metal absorbs energy by changing shape. That's why cars are are built with crumple zones, so that they absorb the energy of an impact. In the 20's cars didn't have these, so in a car crash whatever was inside them (like people, for example) would take all the energy of the impact (and die). Metal armor works just like that.

Steel is good for armor because it has a good mix of hardness and toughness. Yes, toughness, that's a technical term. It means:

(...)the ability of a material to absorb energy and plastically deform without fracturing.

Now, diamonds, emeralds rubys etc. have the wrong mix for it. They are too hard and are not tough enough. Let me explain:

• Too hard: they will not bend nor change shape in any other way to protect you. If you could build an emerald helmet and wear it while I hit your head with a hammer, that emerald will happily transfer all the energy of the impact to your cranium. You'd fare better if you were using a metal elm instead.

• Not tough enough: if people keep saying that emerald would make good armor because it is very hard, I will go hulk-mad and hit you on the head with even more force. If you are still wearing an emerald helmet, at some point it is going to shatter like glass. Not only you took all the kinect energy for yourself (because that precious stone will never take a hit for you), you now have shrapnel in your cranium.

The joins where the metal meets the gemstones would be a weak point, unless there was some technology in play to fuse the two materials into a seamless joint, or the setting of the gem was backed completely by metal. Most settings for gems are literally bands of metal tightly grasping the gemstone (or prongs of metal doing the same). If you damage or dent the metal around it, odds are the gemstone becomes dislodged or falls out and now you have a bigger vulnerability (unless there's sufficient metal behind the setting).

In theory, emerald is harder than iron and steel (and the same hardness as hardened steel), but I think that the joining of the material is the weakness. If it was completely backed by metal of the same thickness as the rest of the armor, it shouldn't be a weakness (or not an easily exploited one).

I think making armor in such a way that it wouldn't be weakened by adding gemstones would add a lot of additional weight to it, and probably make the form of it awkward.

• Hardness is, according to the very wiki you linked to: "a qualitative ordinal scale that characterizes the scratch resistance of various minerals through the ability of a harder material to scratch a softer material". It has nothing to do with toughness or tenacity, for example, which is what you look for when you want to design protective clothing or armor. – Renan Jul 7 '16 at 13:41
• @Renan, that's the wrong wording of hardness for this situation. Here you want: Resistance of metal to plastic deformation, usually by indentation. That doesn't carry over to gemstones as they don't deform plastically so the scratch test applies, but hardness is still the correct term. – Separatrix Jul 7 '16 at 13:46
• If you think the wording is wrong, you may wish to link to this other wikipedia article instead. It has the same description you provided in your comment. My point about hardness not being the defining characteristic for good armor still stands, though. – Renan Jul 7 '16 at 14:13

In general I agree with the other answers that any embedded gem / crystal weakens an otherwise whole armor.

At the same time, gems or crystals or ceramics in general can provide additional protection. Think for example of bulletproof vests which have a ceramic layer inside.

So for example a mix of emerald as a hard ceramic and a soft layer of i.e. silk can increase the protection against, for example arrows or bolts or bullets in comparison to only metal. If the stone breaks during impact the soft layer behind the gem would catch the shrapnels preventing them from entering the body.

Similar approaches, were used by a lot of nations during the medieval times. Think of ringmails. One particular example are the mongols. Those were wearing light armor of leather in combination with hard and light iron elements and underneath silk clothes. This combination was very successful in preventing arrows from entering the body. This apparently also lead to the myth, that silk clothes can be used to remove arrows safely from the body, which I wrongly cited here. Mea culpa.

You can still apply the same principle to stones / ceramics instead of iron. The trick is to introduce multilayered armor.

At the same time, emerald is approximately 2.5 times lighter than steel, which would make the whole armor lighter.

So in a nutshell, if you have an intelligent design concerning the stones, you can actually achieve additional protection in my opinion.

Be aware that hard materials like stones, can still be brittle and break easily.

• Welcome to the site Freddy. If you have questions check out the help center and feel free to join us in Worldbuilding Chat once you hit 20 rep. – James Jul 7 '16 at 14:09
• I have never read about crystals and gems being used additional protection. Can you provide some source? – Renan Jul 7 '16 at 14:15
• @Renan you are correct to assume gems were not used. What I rather meant, was that similar approaches of multilayered protection were designed in medieval times. Gems were and still are too expensive for such a purpose, but the principle can in theory be applied to them as well. – FreddyKay Jul 7 '16 at 14:25
• You know that ceramics don't necessarily have to be crystalline, right? Comparing them to gems is like comparing apples to oranges. – Renan Jul 7 '16 at 14:43
• That is correct. Ceramics come in different forms one of which is for example boron nitride, which is similar to diamond and the second hardest known material afaik. Therefore I think you can indeed compare them. Amorphous ceramics can still be compared to crystals concerning their physical characteristics. – FreddyKay Jul 7 '16 at 14:54

it is tough to say without more details, but the stone would probably weaken the armor very slightly unless it was unrealistically large and pure.

some things to consider:

1. a green saphire would be stubstantially stronger and tougher than emerald.
2. when steel hits it's limit, it bends while absorbing energy. when gems hit their limit, they shatter and/or crack, absorbing substantially less energy.
3. the armor would be weekened at the joint between steel and gem because that interface would be rigid like gem, but soft like steel. re-enforcing that joint would add more weight than you save using sapphire for realistically sized gems.
4. in theory a very large sapphire (e.g. covering the entire chest) could be stronger than an equivalent weight of steel plate. similarly, replacing the entire knee plate with a single well shaped sapphire could be better than the comparable weight in steel. obviously green sapphires this size have never been found on earth. however, modern armored car windows are made from synthetic aluminum oxide, which could easily be made into a green sapphire by adding trace elements.
5. sandwiching sapphire (or even emerald) between two steel plates could provide improved resistance to armor-peircing arrows (and lances). this would be similar to the ceramic plates in modern composite armor. again, this would require extremely large thin plates of gem, and most of the plate would be hidden. although, you could probably reveal a small window of gem without greatly reducing the overall odds of protection. obviously an arrow that hit that window of gem would not be stopped as effectively.
6. steel is superior primarily because it is easy to shape, and can take a lot of damage while still providing protection. if you could somehow (magically?) shape the gemstone into a breastplate, and you made it thick enough that standard weapons could not shatter it, then it would be lighter than an equivalent steel plate. i'm not sure if that would be light enough the wearer could still walk.

I may have missed this in the other answers, but there is another point to consider.

Any protrusion from the armor will provide another way for a spear thrust to catch the armor instead of sliding off. This could be the difference between staying on your horse or being roughly pushed off of it.

Yes, in a few ways.

First off, there's the obvious answers; having gems on you makes people want to kill you and steal your armor to sell the emeralds. The gems also make you heavier.

Then, there's a scientific issue; gems are kinda like a two-edged blade. Gems are all crystals, and crystals consist of repeating patterns. Certain crystals have a weakness where due to a weak bond in their patterns, they will easily split along a certain 3-d axis (a plane). These planes are called "cleavage" planes. Emerald (beryl) has this property; thus, even though theoretically the emerald is far stronger than steel, cleavage means it'll easily shatter if hit right.

Now, this might not be a fatal issue if the gems were simply affixed to the armor, but it'd still cost a lot. But crystalline beryl doesn't have to be in the form of large gems! According to this paper beryl microparticles embedded in aluminum improves its tensile strength, giving us another use for the beryl.