**2.3.3. Fluorbritholite-(Ce)**

The mineral fluorbritholite-(Ce) ((Ce,Ca)5(SiO4)3F) [1],[110]) is the fluorine-rich analogue of britholite-(Ce). The structure and known localities of the mineral fluorbritholite-(Ce) are shown in **Fig. 36** and **Fig. 37**, respectively. The mineral has a yellow, reddish-brown color, or

**Fig. 36** The structure (perspective view along the *c*-axis) and the crystal habit of fluorbritholite-(Ce).


**Fig. 37** The localities for the mineral fluorbritholite-(Ce).

it may be colorless. Its hardness on the Mohs scale is 5. Measured and calculated densities of fluorbritholite-(Ce) are 6.67 and 4.66 g⋅cm−3, respectively.

Fluorbritholite-(Ce) is a very brittle mineral that crystallizes as hexagonal in the space group P63/M. The unit cell shows following crystallographic parameters: *a* = 9.517 and *c* = 6.983 Å, *a*:*c* = 1:0.734, *V* = 547.74 Å<sup>3</sup> and *Z* = 2.
