Note: I have a physics degree and a little bit of condensed matter experience, but nothing like anyone actually working in the field. Just some graduate courses and a bit of lab work experience.
There's nothing more revolutionary than a discovery of a new class of materials. After all, we often name eras throughout our history after them :) (Stone age, etc)
I wonder what was involved in the discovery of stone.
With instruction, it would probably take you less than an hour to learn how to make the types of simple chopping stones that human ancestors used 1 million years ago. However, it takes much more considerable time and skill to learn how to make the types of stone tools humans were using 100k years ago. You get the sense that each group of ancient humans probably had an old expert toolmaker who passed on the trade to the next generation.
Mostly archaic humans hitting rocks against each other until they notice that flint knapping [1] creates a sharp edge.
What makes it difficult?
That would be a wild story if true.
Its not enough to produce the material itself, it seems it is an emergent property of the structure and formation of the material similar to piezoelectric effect?
Wild guess is that the dopant that creates wells doesn't always end up where it should. The paper that claimed superconductivity in layers of graphene at very particular angles also seems to be very sensitive. A similar one claimed graphene with alkanes was observed to superconduct. Perhapes whatever impure hydrocarbon they were using held the sheets at the perfect angle. All the quantum wells these things are claiming to rely on seem terribly difficult to arrange perfectly enough to work consistently. Assuming any of them ever did.
I'd imagine early history of sugar products is the same. Today you can precisely control the temperatures and so you can engineer getting exactly the desired products from sugar, but if you're not so good at either measuring or keeping careful control of temperature, you get... something. It's sugar so in most cases it's delicious anyway, but if you wanted fudge but you've made toffee you may be disappointed. With practice you can "eyeball" it without better equipment, like the cat's whisker, but with better equipment an idiot with no experience can make it do what they wanted because the numbers were correct.
Even an old rusty razor blade will work as a diode if you try hard and long enough.
They had to get pretty creative in their use of ironsand to produce high quality steel.
Notably phosphorus is very hard to get rid of when it's in your metal. Before better metallurgy, the best steel worldwide was made out of low-phosphorus ores.
No, we don't know how to reproduce it, with "we" being everyone not on the South Korean team.
The papers everyone is trying to work from to replicate this are the "leaked" arXiv papers. That actual peer reviewed paper is still in process, and presumably that one includes more information on how to replicate the material.
That's... not easily replicable.
Once we know the exact structure, the problem of synthesis is very solvable.
It's not clear exactly what compound constitutes "LK-99" because the equations in the papers are unbalanced and the synthesis is ill defined. What they say they got doesn't make sense for how they say they got it. Most likely it's a mixture of compounds, any of which could be producing the alleged superconducting phenomena.
I expect things like the cooling rate (which affects crystal growth) and oxidation will both have variability in them.
Is there any hard limitation that prevents synthesizing in bulk? If not, I would not worry about this at the moment and if it proves to be a material with desirable properties just leave it up to the engineers who will hopefully find a suitable production process.
edit to clarify: Bulk here refers to having a single chunk of the material, and does not refer to the total quantity. Some physical properties only exist or only surface in chunks of material, not in the powder form.
Assuming this is real, that would be the obvious process by which to try and build useful conductors and magnets - it also suggests a refinement process (passing it over a magnet would quantum lock superconducting grains and let the rest slide off).