A word to the wise
Unless you use black toothpaste, under no circumstances should you ever inhabit a dwelling that contains a black sink in the bathroom. This advice is based upon bitter personal experience. A white sink may be cleaned with some degree of infrequency; a black one must be swiped much more often and always before a visitor is expected. White residue is not a pleasant visual when viewed against a black porcelain background. The current inhabitants cannot be blamed. This is a pre-existing basin, not one installed after arrival.