Decrespignyite-(Y) is a copper yttrium rare earth carbonate chloride hydrate;[2] Usually found as single pseudohexagonal platelets, often curved, and regularly measuring 10-50μm in size.

Regarded as a supergene mineral which is believed to be formed through by mildly carbonated ground waters precipitating through the ore body.

Natural History Museum, Austria), K. Wallwork (School of Chemistry, Physics and Earth Sciences, The Flinders University of South Australia), and L. Nasdala (Institute of Geosciences and Mineralogy, Johannes Gutenberg University, Germany),[2] to perform the required tests and analyses in order to determine the nature, and properties of this (then) new mineral.

Using a combination of X-ray diffraction, with analysis using a 100 mm diameter Guinier-Ha gg camera (using Cr-Kα1 radiation (l=2.28970 A°) and Si as an internal standard), vibrational spectroscopy gaining Raman spectra obtained by use of a Renishaw RM 1000 system, (equipped with Leica DMLM series optical microscope), and chemical analysis via electron microprobe using a Cameca CAMEBAX SX51 electron microscope, and observations of physical properties; the team eventually determined no other known mineral matched the specimens collected.

The IMA approved the naming, and the status of the mineral Decrespignyite-(Y) (2001-027)[6] during 2001, with the description paper by Wallwork et al. being published later in 2002.