What is "decrespignyite-"

Decrespignyite-(Y) is a copper yttrium rare earth carbonate chloride hydrate;

With a simple formula of; Cu(Y, REE)(CO)(OH)Cl · 2HO

Usually found as single pseudohexagonal platelets, often curved, and regularly measuring 10-50μm in size. It appears as royal blue to turquoise blue in colour, with a pale blue streak, and a pearly to vitreous lustre. Regarded as a supergene mineral which is believed to be formed through by mildly carbonated ground waters precipitating through the ore body. It is often associated with malachite, kamphaugite-(Y), donnayite-(Y) and caysichite-(Y)