The phrase "a rare class of" is correct and usable in written English.
It can be used when referring to a specific group or category that is uncommon or not frequently encountered.
Example: "The researchers discovered a rare class of marine organisms that thrive in extreme conditions."
Alternatives: "an uncommon category of" or "a unique type of".
A rare class of plants called hyperaccumulators combines extremely high tolerance degrees and foliar accumulation of trace elements.
Ataxites are a rare class; of the 49 iron meteorites whose falls have been observed, none is an ataxite.
It is aimed at a rare class of people in specific circumstances... Bertrand Russell was absolutely right when he called The Prince "a handbook for gangsters".
Adult granulosa cell tumors (AGCTs) are a rare class of ovarian tumors with recurrent cytogenetic abnormalities including trisomy 12, trisomy 14, monosomy 16/deletion 16q, and monosomy 22.
Much of my work focuses on "superluminous" supernovae, a rare class of transients 10-100 times brighter than ordinary core-collapse and Type Ia supernovae.
He gave these deviant proteins an exotic name, prions (pronounced PREE-ons), and established that they cause a rare class of degenerative brain ailments: Creutzfeldt-Jakob disease for one and, more important, bovine spongiform encephalopathy.
For example, expanding this app to allow users to attach custom graphics to their custom actions would create a new, rare class of virtual objects.
Hoag's Object, located 600 million light-years from Earth, is one of the most famous of a very rare class of galaxies known as ring galaxies.
Other meteorites of a rare class called shergottites had a similar origin from Mars.
However, pyrrolidine alkaloids carrying an aromatic substituent on the ring are of a rare class found in nature [ 12].
The problem, he says, is there still needs to be an unusually powerful engine driving the ejecta, so 2005ap could represent a new and rare class of supernovae.
