What are supernovas made of?
The same thing all stars are made from, hydrogen and helium.
All stars start out as hydrogen which through intense gravity start the process of nuclear fusion. Nuclear fusion in this case is two atoms of hydrogen are fused into one atom of helium. This process goes on for the entire life of the star.
Our star, the sun, for example, will never go super nova. Towards the end of its life it will quickly expand into a red giant before collapsing into a white dwarf.
A star roughly 8 times the mass of our sun and greater will almost certainly go to super nova.
Stars relatively the size of our sun will continue to combine elements until the element of iron, element number 26, is produced at which time all nuclear reaction stops.
Those large stars which go super nova, their gravity being too great, continue their nuclear fusion through the entire spectrum of natural elements on the periodic table. The heaviest elements are at the star's core and the layer outward have lighter metal up to the edge.
When the star finally goes super nova, blows up, all the elements it has created are shot out into space. And so, when you see gold and silver, you are seeing elements which were created by a super nova millions if not billions of years ago.