Minerals are combinations of chemical elements arranged into crystalline structures. Earth's rocks are built from different aggregations. Think of feldspar, quartz and mica - these are the ubiquitous species that everyone knows.
But cobaltominite, abelsonite, fingerite, edoylerite - these are examples that will not form unless the "cooking conditions" are absolutely perfect.
The atomic ingredients must sum exactly, the temperature must be precise to the degree, and the pressure will have to be defined in the narrowest of margins.
And then, some will immediately fall apart when they get wet or the sun shines on them.
Nevadaite, pictured below, is only known from just two locations: Eureka County, Nevada, and a copper mine in Kyrgyzstan