The premise of this suggestion is as follows: 1. Resemblance of realism (believability) is GREAT even in fantasy/soft sci-fi settings when it does not hurt gameplay and/or beneficial to it. 2. Horizontal branching is awesome, linear vertical tiers are somewhat boring. Tier 0: Neolithic. Items crafted from bone, wood, stone, leather. Notice that not everything which is crafted from leather or any other of these materials are automatically crap. For example, Florans may have interesting schematics for weaponry made of hi-tech metal PLUS bone, leather or even meat. But in general, for other races - yeah, this is the last resort and basically the worst. No actual reason to craft this, except for appearance maybe. Tier 1: Bronze Age. Basic metal: Copper. Plentiful, existing even on surfaces of most planets. Additional metal: Tin. More rare than copper, but readily available. Alloy: 2 Copper Ingots + 1 Tin Ingot = 1 Bronze Ingot. Yeah, some material go out as a waste, and this may be fixed by more advanced smelting facilities, meaning that 2+1=1 is low-tech default value. Copper items should be poor beginner's equipment. Basics, necessities. Obvious. Tin may not be used for crafting equipment, only some decorations - also look further. Bronze is a rich beginner's equipment. Way more powerful than copper one, comparable to basic stuff of the next tier. Comparable meaning either similar to 5-10% or perhaps even better in some statistics in certain cases. Late game usage. Copper: should be used in many if not all electric/electronic appliances. Tin: more niche, certain items (not exactly equipment, more likely industrial appliances) may require good amounts of tin. Bronze: mostly decorative, it looks just great! Tier 2: Iron Age. Basic metal: Iron. Most if not all planets, including beginning ones, should have some iron. Way more plentiful near the core. Additional material: Coal. Two ways to get: mining and burning wood. It does not appear everywhere, it is not very deep, and it lays in really huge clusters. So it is either no coal or lots of coal. Burning wood is self-explanatory, with more advanced furnaces producing more coal per wood. Alloy: Steel. 2 Iron Ingots + 1 Coal Lump = 1 Steel Ingot. Similar to bronze, value may become better with more advanced smelting facilities, and this fact won't be repeated for next tiers. Similarly to tier 1, Iron items are poor t2 explorer substitute for Bronze, while Steel is pretty good. Now it gets more interesting. Quenched Steel: Special quenching crafting "table" should be used for this process. Basically, take prepared common Steel item and put it there. There is a chance that it'll break, which can be mitigated by expanding on "table", using additional structures and perhaps oil instead of water, which is consummable for this process. If successful, item upgrades noticeably. Perhaps this technology is behind a quest wall, but maybe not, quenching was known to ancient Romans, I'm sure most of the spacefaring people may figure this out. Wootz: 2 Steel Ingots + 4 Coal Lumps = 1 Wootz Ingot. Require special smelter. Can be substituted for basic Steel Ingot in most weapon/armor schematics to craft items of way better quality. This is tier 3 level stuff, very powerful, but costly to craft - and, perhaps, it is behind a schematic/quest wall, so not possible to craft for everyone. Late game usage. Alloyed Steel: 2 Steel Ingots (no Wootz, that stuff is special) + 1 Ingot of Copper, Silver, Titanium, Tungsten or maybe other metals = Copper Alloyed Steel, Titanium Alloyed Steel et cetera. Variable powers for equipment wrought from these materials. For example, Silver Alloyed Steel may be awesome for "magical staves" but may actually be way worse for armour, and Titanium Steel is the other way around. Notice that certain materials which may be used to create alloy may be from way higher tiers. This is intentional: make steel relevant for most if not all of the game! Look around - the world is MADE OF STEEL. Thus, another late game usage for steels of all sort - hard building blocks and various industrial appliances. Steel roofs should be resistant to meteorites, alloyed steel roofs may be immune. Tier 3: Industrial Age. Basic metal 1: Aluminum. Very rare on most worlds, BUT can be crafted from LARGE amounts of DIRT in high-tech facility. About 100 Dirt per 1 Aluminum Ingot. This is the fine way to remove excess amounts of Dirt which everyone have. Basic metal 2: Titanium. Rare, it is found in trace amounts and somewhat more plentiful at mid depths, but not close to the core. Also rarely may appear as subproduct of Dirt-to-Aluminum refining. Basic metal 3: Tungsten. Deep, close to the core. Basic metal 4: Lead. Abundant material which may be found near Gold almost everywhere. All three of these metals may be alloyed to steel, and this is true to all other metals in the game, so won't be mentioned anymore. Aluminum items (just as aluminum alloy steel to some extent) are weak, but light. Probably best for ranged characters. Titanium sounds magical, so it will be cool material for a staff-user. Also nice fast melee weapons. Tungsten could be inherently heat-resistant, best for melee character and perhaps for some staves. Lead, like Tin in Tier 1, is not for crafting of basic equipment, but it may be required for making most gunpowder-based weapons due to obvious reasons. Also blocks of Lead and materials based on Lead protect from radiation completely, which may be nice for some worlds near hostile stars. Durasteel may be the name for a special, quest-locked alloy of titanium, steel and tungsten. And it should be awesome. And there should be alloys of Durasteel and other metals. Late game usage. Aluminium and Titanium are awesome vehicle-building materials. Tungsten is for heavy industry. For example, tungsten-reinforced ceramical smelter sounds like it is really efficient. Tier 4: Nuclear Age. Basic metal 1: Osmium. Ultra-rare, it is better to buy it from vendors than to try to harvest it. Finding a vein of Osmium should be a joy. Deep only, exists not on every world. Perhaps there could be rumors like "there supposed to be a lost crate of Osmium on a crashed contraband vessel at the planet Wherever II". Notice that while very rare and hard to obtain, it should not be critical to progress. Basic metal 2: Uranium. Kinda plentiful, useful, but extremely dangerous. Each block of uranium ore emits damaging radiation, which makes getting close to large enough veins potentially fatal without good protection. Oh, and Osmium is the way to protect properly. You may use cheap substitute made from Lead, and it works on all applications of Osmium. Basic metal 3: Thorium. Softcore version of Uranium, not radioactive enough to damage, or with weaker radiation. Uranium sounds good for projectile-based weaponry. Osmium is magic, and Thorium is melee. In general. On the other hand, Uranium and Osmium, being way harder to obtain than Thorium, should have more interesting properties. Late game usage. Alloys, nuclear and more advanced facility making. Tier 5: Fantastic Age. And this is the time to add fantastic elements such as Rubium et cetera. Again, Rubium Alloyed Steel sounds interesting, Rubium Alloyed Durasteel is probably even better, and there may be a way to produce Impervium, making it completely awesome. I don't feel that there is a necessity to detail this tier at the moment, because it is out of the premise boundaries. Notice that because these elements are fantastic, perhaps they should not be easily mineable even on hard worlds. It feels better to find this stuff by scrapping advanced alien technological marvels or something like that. Also, perhaps there is no Rubium or Impervium craftable equipment, it is still Alloyed Steel or Alloyed Durasteel. Although at this point there should be possible to obtain trivial minerals such as Coal, Iron Ore or even Tier 3 metals in some ways beside manual mining - perhaps by hiring a miners or by purchasing this stuff in bulk for reasonable prices. Late game usage - this is late game.