The Collaborative International Dictionary of English v.0.48:

Pleonaste \Ple"o*naste\, n. [Gr.? abundant, rich; cf. F.
   pl['e]onaste.] (Min.)
   A black variety of spinel.
   [1913 Webster] Pleonastic

The Collaborative International Dictionary of English v.0.48:

Ceylanite \Cey"lan*ite\, n. [F., fr. Ceylan Ceylon.] (Min.)
   A dingy blue, or grayish black, variety of spinel. It is also
   called pleonaste. [Written also ceylonite.]
   [1913 Webster]

WordNet (r) 3.0 (2006):

pleonaste
    n 1: a dark-colored spinel containing iron [syn: Ceylonite,
         pleonaste]