What are the favourable qualities given to gold when it is alloyed with copper or silver for the purpose of making ornaments?

Pure gold is a very soft metal and is very ductile and malleable. Thus, it can be given any shape and it can also break by applying a little force. Therefore, it is not suitable for making ornaments. Pure gold, when alloyed with copper or silver, becomes harder and stronger it will not break on applying even a little force. Thus, it becomes suitable for making ornaments.