A new elemental plane

I'm gonna go the route of Chinese elements and say that a Plane of Metal would be pretty awesome.

It would be like Acheron, but cooler. Wouldn't metal elementals be the most awesome thing ever?

And speaking of coolness... why not the Elemental Plane of Coolness?

It's hard fitting anything new into the existing Inner Planes structure because it's so damn symmetrical. If you add Wood or Metal as separate plane you'll have to add 2 more antithetical planes to the equation so that everything balances.

If you did Chinese Inner Planes, you could still have Quasi-planes, but I don't think the Para-planes would work anymore.

Or you would need a very different para-elemental structure. Something where each plane touches two neighbors and Earth, in the middle, touches all four of the other planes.

Metal > Water > Wood > Fire > Metal

Metal + Earth = ore? mineral?
Water + Earth = Ooze
Wood + Earth = soil?
Fire + Earth = Magma
Metal + Water = quicksilver?
Water + Wood = ?
Wood + Fire = coals?
Fire + Metal = erh, molten metal?
Metal + Positive = something really similar to Mineral?
Metal + Negative = Rust (and tarnish)
Wood + Positive = growth?
Wood + Negative = Rot

You could move Mineral to be the positive quasi-Metal, and make the positive quasi-Earth something else, such as Obsidian.

The wu jen class (from Complete Arcane) uses the five Asian elements as a school structure and introduces several metal spells to fill out that list from those available already. They might even perceive the Inner Planes in this fashion already!

A quick glance at Wikipedia reveals to me that there are two different interaction systems: one "generating", in which one element creates another, and one "overcoming," in which one element lessens another. Instead of having quasi- and para-elemental planes, then, perhaps you could have more dynamic Generating and Overcoming planes, combining aspects of the quasi- and para- divisions.

Picture, then, the five elements arranged in a ring: Wood, Fire, Earth, Metal, Water. On the pole above them is Yang (positive energy) and on the pole below them is Yin (Negative Energy). Truth to tell, of course, there's no such direction in the ethereal: every elemental plane in this arrangement shares a border with every other elemental plane, even Wood with Earth and with Metal. You could arrange the ring Wood, Earth, Water, Fire, Metal, and in so doing more clearly show the arrangement of Overcoming planes, which normally have to be shown on a separate map for two-dimensional mapmakers, or hung between the planes in the shape of a pentacle for three-dimensional orreries.

So we'd have the following ten, oh, let's call them hemiplanes:

Generating Hemiplanes:

Wood generating Fire: Hemiplane of Air. Winds rustle through reeds and shake branches as you pass toward the plane of Fire; gradually, the winds become faster, the grasses dry out, the branches rub harder... and then they burst into flame all around you. (There seems to be a large inhabited portion of this plane far away from any wood at all. How very strange, think the wu jen.)

Fire generating Earth: Hemiplane of Coals. Follow the cinders as they collect, from specks into rivers of red-hot boulders, cooling and solidifying into a wall in front of you. Rich ash fertilizes the soil that surrounds you, volcanic obsidian glimmers. (Negative energy? When ash is so good for plants and volcanos create whole islands? What strange notions foreigners have of the elements. This plane is touched by Yang, not Yin.)

Earth generating Metal: Hemiplane of Ore. Gems are pretty, yes, we see why you call this the Plane of Mineral, but really, ask any dwarf and he'll tell you it's the veins of metal he's after here.

Metal generating Water: Hemiplane of Rain. Down it pours from pure Yang, gentled into droplets by the elemental nature of Water, to be collected here by Metal and poured into its native plane.

Water generating Wood: Hemiplane of Muck. Yang enriches water with nutrients, which thicken until you slow from swimming to a crawl through mud and lush soil oozing with vitality, to emerge in the great forest of the Plane of Wood.

Overcoming Hemiplanes:

Water overcomes Fire: Hemiplane of fumes. You can get from Water to Fire, if you're willing to pass close to Yin, and go through a choking hemiplane of gradually dirtier steam and smoke to get straight to your destination.

Fire overcomes Metal: Hemiplane of Magma. Metal in this plane has fallen under the relentless assault of fire. It may be a necessary step in the process of purification, but the wu jen can be uncomfortable so near a manifestation of Yin. (Even if you don't think the plane is near Negative Energy at all.)

Metal overcomes Wood: Hemiplane of Vacuum. To travel from Metal directly to Wood, you must pass in the track where the blade has struck, through this plane the wu jen call the Wound. Launch yourself from the point of the metal's wedge; if you know the way, you will land in a notch of wood on the other side.

Wood overcomes Earth: Hemiplane of Dust. Travel to where the forest thins, where Wood has taken the nutrients it needed from Earth, and in this border region you see the dry, lifeless dust that is left behind. To dig down here is the fastest route from Wood to Earth, but don't hope for a pleasant trip.

Earth overcomes Water: Hemiplane of Salt. If you must cross the abyss between Earth and Water without passing through Metal, you will pass through the realm where the Earth has sucked up the water that reached it.

This is also a possibility, since the other four elements are associated with directions: wood in the east, fire in the south, metal in the west, and water in the north, while earth is associated with "center." However, it does give Earth a certain primacy.

Quintessence is the substance of the Ethereal, which works nicely as the plane where the inner planes intersect.

I honestly never understood why there wasn't a quasi-plane of wood in place of mineral. Seriously, while the idea of an entire infinite plnae of precious gems and stones is ironically awesome, it also creates a lot of serious issues. The existence of such a plane could very well cause a collapse of the entire economical system. I think Mineral is a randomly occuring "geographical feature" of the Earth, and it increases in frequency towards core earth.

Another interesting plane, though more fitting to Urban Planescape maybe, would be an elementa plane of fossil fuel: An elemental plane of oil and gas. Though the end result would be the same economical collapse of mineral, it would fit the theme of the setting

I like the idea of a Plane of Plastic - reminds me of a George Carlin monologue ("Why are we here?" "PLASTIC, ASSHOLES!").

On the other hand, how about a Plane of Wine, or more generically, Alcohol? Would that be a popular destination or what? Just make sure you can distinguish the ethanol from the harder stuff!

The existence of such a plane could very well cause a collapse of the entire economical system.
Well, luckily that's countered by the angry natives who REALLY hate it when non-natives take pieces of their land home. Also, they organize themselves like armies, so defeating them isn't easy. Oh, and don't forget the Dao.

The plane of Mineral is mainly crystal (quartz, lead, etc.), as I see it, with precious gems and metals extremely rare.
Actually, the way I see it is that it's a plane primarily of quartz and ferrous metals, with precious metals and minerals being uncommon. "Extremely rare" is more how they're categorized on Earth. Also, like I said, Inner Planes sets it up so that the DM can plot-device a way to keep the PCs from profiting big-time off of it and destroying their base city's economy. It's also likewise set up so that the DM can allow an exception in the case of a quest where a special material from Mineral is needed.

Gas and fossil fuels would be a sub-region of Ooze if anything. It's the only plane that consists in large part of organic matter, and some areas are highly pressurized.

I think the second really explains it way better than the first, honestly. The elemental planes are infinite so far as I'm aware, and so I'm pretty sure there's a 100% chance that at any given moment there's an area empty enough of locals for someone to snatch a few goods and move on to the next one.

Though actually I suppose that means that even if a randomly selected region is (some huge but not quite 100)% quartz and ferrous metals and the rest is precious metals and minerals, that there's still an infinite quantity of the latter to collect.

Has there ever been a solid statement about the population of the inner planes, are the number of elementals infinite as well? I mean, it's entirely reasonable to assume so (although that runs into its own weird side effects), but has anything ever said for certain that there are or not?

(This gets me thinking about other stuff too, but I'll split that into a separate thread.)