The accepted image of muscovite mica is that of an inert and atomically smooth surface, easily prepared by cleavage in an ambient atmosphere. Consequently, mica is extensively used a model substrate in many fundamental studies of surface phenomena and as a substrate for AFM imaging of biomolecules. In this review we present evidence from the literature that the above picture is not quite correct. The mica used in experimental work is almost invariably cleaved in laboratory air, where a reaction between the mica surface, atmospheric CO₂ and water occurs immediately after cleavage. The evidence suggests very strongly that as a result the mica surface becomes covered by up to one formula unit of K₂CO₃ per nm², which is mobile under humid conditions, and crystallises under drier conditions. The properties of mica in air or water vapour cannot be fully understood without reference to the surface K₂CO₃, and many studies of the structure of adsorbed water on mica surfaces may need to be revisited. With this new insight, however, the air-cleaved mica should provide exciting opportunities to study phenomena such as two-dimensional ion diffusion, electrolyte effects on surface conductivity, and two-dimensional crystal nucleation.

白云母云母的公认图像是惰性且原子光滑的表面，可通过在环境大气中裂解而容易地制备。因此，在许多表面现象的基础研究中，云母被广泛用作模型基质，并作为生物分子AFM成像的基质。在这篇综述中，我们提供了来自文献的证据，即上述图片并不完全正确。实验工作中使用的云母几乎总是在实验室空气中裂解，在裂解后立即发生云母表面，大气CO ₂和水之间的反应。证据非常有力地表明，结果云母表面被每nm ²最多一个公式单位的K ₂ CO ₃覆盖。，在潮湿条件下可移动，在干燥条件下可结晶。如果不参考表面K ₂ CO ₃，就无法完全理解云母在空气或水蒸气中的性质，因此可能需要重新研究云母表面吸附水的结构。然而，有了这种新的见识，空气裂解的云母应该为研究诸如二维离子扩散，电解质对表面电导率的影响以及二维晶体成核等现象提供令人兴奋的机会。