Pyrite can be found in the form of cubic crystals. The shape is dependent on the concentration of sulphur during the formation of the cystals. See the pictures of the pyrite crystals from Navajún, Spain: http://www.therockgallery.co.uk/pyrite-crystal-individual-cubic-crystal---spain-733-p.asp

This is an interesting question. In addition to the very good observation by @ Keith Jones, there is a bit more to add.

There are many forms of cubical shapes and cuboids in nature. Here are examples.

Diamonds:

Naturally occurring cuboids occur in diamonds. See, e.g.:

Article Nitrogen and hydrogen aggregation in natural octahedral and ...

Graphite:

Conference Paper Petrologic and crystallographic nature of cuboid graphite fr...

Isothermal cuboids:

Article Natural convective heat transfer from isothermal cuboids

Thank you Prof. Keith and Prof. James.

It is interesting that crystals are having cuboids in nature. I observed the following as well.

Let us denote set of all cuboids and polygonal shapes man made (now we can include natural one) in the universe by A and set of all spherical, conical, cylindrical, irregular shapes by B.

1. A is almost nothing compare to B.

2. In atomic level, A will be a subset of B.

It is a Conjecture.

Interestingly, Vacuum stands over there to compete them.

For a detailed answer look for the research of Gábor Domokos for example in the project: https://www.researchgate.net/project/Morphology-and-equilibria-of-rigid-bodies-from-theory-to-applications

There is a classification of pebbles there.

Dear Panchatcharam Mariappan,

You forget to mention the most important type of the amazing geometrical shapes, the fractals.

In fact, fractals are everywhere in nature

As well what about the shapes that are (living things) made.

Watch the great engineer, the spider.

The nest of the birds, all creatures, even the insects have their incredible geometry. In which category they should be A or B?

I think this will enlarge the set A versus the set B.

Finally, I would like to add, topology unified almost all into similar categories, where the cube and the sphere are living in the same class.(Homeomorphic)

Best regards

Curves are more frequent phenomena for the world of nature. They have important feature of 'repeatability' that can often be found in the fractal patterns from micro to macro scales.