The phrase "are commonly formed" is correct and usable in written English.
It can be used when discussing how certain things or concepts are typically created or established in a general sense.
Example: "In nature, crystals are commonly formed under specific temperature and pressure conditions."
Alternatives: "are often created" or "are frequently established".
Sole marks are commonly formed on sandstone and limestone beds that rest upon shale beds.
Israel's party system has traditionally been complex and volatile: splinter groups are commonly formed, and party alliances often change.
Under the reaction conditions employed, four iron oxides are commonly formed.
Nanoparticles are commonly formed by self-assembling of amphiphilic polymers in aqueous environment.
Surface pits are commonly formed where threading dislocations emerge from a thin film.
The sugar dehydration products, furfural and 5- hydroxymethyl)furfural (HMF), are commonly formed during high-temperature processing of lignocellulose, most often in thermochemical pretreatment, liquefaction, or pyrolysis.
The classic example is the rock called hornfels, which is formed at contacts with igneous intrusions and in which heat and fluids from the intruding magma reconstitute the original wall rock into a hardened, flinty rock with a dense texture; it also is commonly formed by induration of carbonate sedimentary rocks and shales.
Stress degradation study data showed that peak with Rf 0.01 was commonly formed under all stress conditions.
Degraded product with Rf 0.01 was commonly formed under all stress conditions while degraded peak with Rf 0.02 was observed only under alkaline hydrolysis (5N NaOH).
A UC phosphor is commonly formed by doping a host lattice with a sensitizer/activator pair, where the sensitizer is usually Yb3+ and the activator is frequently being Ho3+, Er3+, or Tm3+.
In nature, singlet oxygen is commonly formed from water during photosynthesis, using the energy of sunlight.
