The absence of blemishes (spots, pimples, cracks) or discoloration on the pearl's surface.

Cleanliness is the absence of dirt, including dust, stains, bad smells and clutter. In more recent times, since the germ theory of disease, it has also come to mean an absence of germs and other hazardous materials. A recent shift has now taken place to recognise that ‘dirt’ may play a useful role in our immune systems.

the Directory adopts the US system specified by the numerical limit of 0.5 µm particles per ft3 (0.028 m3). Thus a class 10,000 environment has fewer than 10,000 particles of 0.5 µm in 1 ft3 (0.028 m3). Most satellite and launcher integration and testing facilities are class 100,000. Class 10 and class 100 facilities are used for assembly of sensitive items such as gyros

the habit of keeping free of superficial imperfections

diligence in keeping clean

State of being cleanly; neatness of person or dress.