Why foids lack good cleavage ChainCountry code: us, country type: geoip, valid: 1 No.24159
Feldspathoids are framework silicates, like feldspars, but their frameworks are more “collapsed” or distorted to accommodate larger alkali cations and sometimes additional anions (e.g., Cl⁻, SO₄²⁻, S²⁻) with lower Si:Al ratios. In feldspars, the Al/Si ordering and the resulting charge distribution create planes of relative weakness — hence the two perfect cleavages at ~90°. In foids, the framework topology is different (e.g., the stuffed tridymite-like structure of nepheline, the complex cage structure of sodalite-group minerals, or the framework of leucite). These structures simply don’t have continuous planes of weak bonding that would allow clean separation. Instead, the bonding strength is more isotropic within the structure, so when stressed beyond its limit, it breaks by fracturing.
t. DeepSeek
