Crosses have an enormous cultural and religious significance in our history. While in Christianity it represents the connection between man and God, it was used especially in the Middle Ages as a representational element in the design of coats of arms or components.
Blackline® is black jewelry, they are not "colored" black in the classic sense, it is 316L Steel or Titanium that is covered with a thin plasma film (PVD coating). The thin film is very strong and does not fade. The technology has been used in the medical industry since the late 80's and is used, among other things, for pacemakers and orthopedic implants to provide an extra durable surface.