Does Silicon Valley has
a lot of silicon?

Does Silicon Valley has a lot of silicon?
Maybe, may not be. But, it is not important!

What important is that Silicon Valley have a lot of silicon related business. (ie. computer related)

See the following map which is from BusinessWeek August 97 and you will find that there are really a lot of well-known computer businesses in Silicon Valley:
(The original map spans 4 full pages. I scale it down a lot already. But, in order to keep the text visible, I cannot make it smaller.)