Apple gold
Reading<p><a href="http://en.wikipedia.org/wiki/Metal_matrix_composite" rel="nofollow">http://en.wikipedia.org/wiki/Metal_matrix_composite</a><p>"MMCs are nearly always more expensive than the more conventional materials they are replacing. As a result, they are found where improved properties and performance can justify the added cost. Today these applications are found most often in aircraft components, space systems and high-end or "boutique" sports equipment."<p>So it seems the goal was really first to have the more durable material.