Are non-Catholic marriages valid in the eyes of the Catholic Church?

In general, marriages between non-Catholics, of whatever religion, are considered valid, but the situation is not as simple as it sounds because there are two kinds of marriage: natural (ordinary) marriage and supernatural (sacramental) marriage. Supernatural marriages exist only between baptized people, so marriages between two Jews or two Muslims are only natural marriages. Assuming no impediments, marriages between Jews or Muslims would be valid natural marriages. Marriages between two Protestants or two Eastern Orthodox also would be valid, presuming no impediments, but these would be supernatural (sacramental) marriages and thus indissoluble.