'Bichrome' is the key. The term is used by archeologists and preservationists. The pieces are typically larger than you see in a mosaic.

(How do I know? My husband was a historic preservationist.)

https://books.google.com/books?isbn=0393730379
Paloma Pajares-Ayuela - 2001 - ‎Architecture
The shift from opus tessellatum to opus sectile in the isotropic geometric ... of the **"bichrome mosaic"** {opus tessellatum in two counterchanged colors) and, in the ...

https://finds.org.uk/database/search/results/objecttype/Tile...
Records 1 - 20 of 54 - ... **Late Medieval-post medieval bichrome, glazed ceramic floor** tile AD ... The decorated surface of the tile depicts a floral central design, ...

https://books.google.com/books?isbn=0892361816
The Getty Conservation Institute - 1991 - ‎Art
**design, floor band, bichrome design**, wainscot, colored wash, dado, de facto plaster, undecorated plaster, and absence of plaster [21]. The condition of the ...

https://books.google.com/books?isbn=0521002303
Katherine M. D. Dunbabin - 1999 - ‎Art
Polychrome designs frequently use illusionistic three-dimensional motifs, some ... floors, creating the effect of a ceiling design reflected on the floor.9 Excellent ... **Black-and-white (bichrome) ornamental mosaics** also developed in the last ...

https://books.google.com/books?isbn=9774246748
Zahi A. Hawass, ‎Lyla Pinch Brock - 2003 - ‎History
**As there is another, earlier mosaic floor below our mosaic, this would indicate that ... Another example of similar design is provided by a second century CE floor ... On the other hand, our piece fits very well into the bichrome, mostly black and ...**