What’s the most recent new type of rock that was discovered? Are there types of rocks out there waiting to be discovered, whether on Earth or elsewhere? Could any of them have exotic or useful properties? Are there theoretical types of rocks that probably exist, but we haven’t seen them? Can new types of rocks be created in a lab?
You mean, like, concretes or ceramics? New types are invented all the time.
Cool! So what’s the most recent significant one discovered?
Yes. There’s believed to be planets that have significantly different elemental abundances and environments than Earth (carbon planets being one example), and would therefore have different minerals. On top of that we see even on Earth that unusual conditions can create rare minerals; if those particular conditions couldn’t happen on Earth, then neither can the mineral.
This wouldn’t at all surprise me. Especially in regions beyond the earth, different conditions exist for the formation of rocks, and some lunar rocks, for instance, have properties that differ from similar rocks on earth.
Biogenic Rocks are made partly by living organisms. Limestone, made from seashells, is a good example, although there are other, subtler cases. It’s not hard to believe that different forms of life, possibly in very different environments, might produce completely different “alien biomorphic rocks”.
So I don’t doubt that there probably exist all sort of rocks that we haven’t encountered before, produced by locally different circumstances, histories, and chemistries, not only on earth but out inspace.
The same elements exist in space as here, so novel space rocks will be new variations on familiar Earth petrology, rather than something utterly strange like kryptonite. For example, novel moon rocks turn out to be new variants on “diorites, monzodiorites, and granophyres … quartz, plagioclase, orthoclase or alkali feldspar, rare mafics (pyroxene), and rare zircon.” Feldspars especially, like plagioclase and orthoclase, form a solid solution phase diagram that allows for infinite variation of composition.
There is a practically unlimited number of potential rock types, a rock being “In geology, rock (or stone) is any naturally occurring solid mass or aggregate of minerals or mineraloid matter.” (from the Wikipedia entry). Any place with any condition that mixes together two or more types of minerals in a way that hasn’t been described before, that’s a new type of rock.
Plastistones are a pretty new recognized category.
Of course – but there are almost infinite possible variations of basic recipes.
That’s not to say that weird stuff unlike anything on earth might not exist, like ultraheavy stable isotopes, like in Preston and Child’s The Ice Limit. But I wouldn’t count on it.
Don’t also rule out “rocks” that only exist in areas outside our regions of experience – things that can only exist at extremely high pressure or extremely high heat, or both.
Depends on your definition of ‘rock’. Wiki says a rock is “any naturally occurring solid mass or aggregate of minerals or mineraloid matter”. So new minerals and mineraloids can be created in the lab but not rocks by that definition. However, the definition includes aggregates and there is an incredible number of different rocks that form on earth alone from combinations of minerals.
Keep in mind that the rocky planets are all made up of exploded star material, the heavy elements within a large star that are ejected in a super nova explosion. That being said, I wouldn’t expect there to be dramatic differences in the rocks/elements found on other planets.
The other side of the coin, however, is that very large stars create more pressure and could possibly form elements with which we are not yet familiar. We need to go out there and fine out! 
To a geologist a rock isn’t simply a type of something. It is a story. And a puzzle to discover the story.
Rocks are created by a myriad of processes, and may involve the presence of elements in essentially any combination. Some more common than others. The exact set of processes and their parameters, be they heat, pressure, chemical reaction and so on will affect the nature of the outcome in highly specific ways. The skill is to tease out the story that gets you the rock you have.
Common processes get you rocks with common names. Rare processes and ingredients, yielding rare specimens, the outcomes get names if they are important for some reason. As stepping stones (pun intended) on the way to understanding local geological processes all of this is highly valuable. It is via understanding these processes that geologists can begin to divine what happened, and thence predict where the money is to be made.
But more than simply following the money, the science of geology is very much a worthwhile end in and of itself. It does tend to live outside of most people’s radar. Which is a great pity.
The simple answer to the OP is a big No. We can be sure that the universe will surprise us with all sorts of unexpected possibilities. We scratch around of the surface of part of our planet, and dig a few holes. There will much more yet.
Thanks for a great answer.
I hope @MrDibble can chime in.
That is a very good basic explanation of the science of geology (versus just sorting and categorizing identified types of rocks), and to make an analogy to zoology, the question of the o.p. is like asking “Do we know all the species there are?” The answer to that is, no, not only because we have certainly not encountered and categorized all possible animal species but also because new species can emerge, or we can (somewhat arbitrarily) redefine animals that were once considered cladistically similar to be distinct species or subspecies.
There are almost certainly types of rock in the crust-mantle interface that do not exist on the surface because they experience pressure and temperature conditions that don’t occur on the surface, and ‘exotic’ minerals found on exoplanets and moons like radical phases of various ‘ices’ that don’t every occur under terrestrial conditions, like the many phases of ice (which, yes, is a mineral). So, even given the finite range of naturally occurring chemical elements, there are such vast permutations of possible mineral configurations that we have most certainly comprehensively catalogued all possible types of rock. Which, frankly, is one of many reasons to support the essentially cancelled Mars Sample Return mission.
Stranger
Probably plastistone like Darren said.
Note that this doesn’t conflict with what I say right at the end of this post - this rock is naturally-occurring even if some of its components are man-made.
Sure, anything’s possible. I mean, something like diamonds are flung from the depths of the Earth, it’s possible there’s something else waiting down there that might be as useful. Not that we necessarily should want it to come up…kimberlite eruptions were very violent supersonic events.
Yep. Plenty of stuff that should, in theory, exist deep in the mantle/core but have never made it to the surface, like post-perovskite.
No, that goes against the very definition of a rock. “Naturally occurring” is baked in.
Thanks!
What weird properties can rocks have, and are there any theories or interesting hypotheses about weird or useful properties of theoretical, undiscovered rocks? For example, could there be a rock out there that could help us build something like the space elevator? Or fusion reactors?
I’m going to say “no”. For those, you’re talking exotic matter, and that’s not going to occur as rocks, I’d say.
A naturally occurring true metal-ceramic matrix would be somewhat rocky and an unexpected find.
You seem to be thinking elements or compounds or minerals, not rocks.
As recently as 2022, a new allotrope of carbon was discovered, called pentaheptite carbon, with properties similar to but not quite the same as regular diamond.
If you can get new crystal structures of even pure elements, then you can most certainly make new kinds of rocks out of them.