What is the composition of an asteroid in percentages? I am developing a RPG game (or so I like to tell myself) within outer space. Within the game, players would be able to mine small asteroids and collect resources, in order to make money. I'm having some difficulty determining exactly how much of the resources there would be in relation to everything else gotten from the asteroid. 

This image has provided me with a good idea of what asteroids generally contain. It does not, however, show me the quantities. For example, I'm fairly certain that an asteroid would have more oxygen than palladium, but I don't know by how much. 

Question: Can someone tell me (or better yet show me) the percentage of materials within an asteroid? I realize not all asteroids are the same, so categorizing or averaging is fine. The more detailed the better. The ideal information would be a list of values that I can scale with asteroid size.
You might find the information you seek in this article by Nature on the compositional mass distribution of asteroids.



From Wikipedia Asteroid Spectral Types:


  The majority of bodies fall again into the three broad C, S, and X
  categories, with a few unusual bodies categorized into several smaller
  types:

C-group of carbonaceous objects including:[citation needed]
    B-type largely overlapping with the Tholen B and F types.
    C-type the most 'standard' of the non-B carbonaceous objects
    Cg Ch Cgh somewhat related to the Tholen G type
    Cb transition objects between plain C and B types.
S-group of silicaceous (stony) objects including:
    A-type
    Q-type
    R-type
    K-type a new category (181 Eucharis, 221 Eos)
    L-type a new category (83 Beatrix)
    S-type the most 'standard' of the S group
    Sa, Sq, Sr, Sk, and Sl transition objects between plain S and the other types in the group.
X-group of mostly metallic objects including:
    X-type the most 'standard' of the X group including objects classified by Tholen as M, E, or P-type.
    Xe, Xc, and Xk transition types between plain X and the appropriately lettered types.
T-type
D-type
Ld-type: a new type with more extreme spectral features than the L-type
O-type a small category (3628 Božněmcová)
V-type (4 Vesta)



You will have to go to the Wikipedia article to drill down for more detail on the probable minerals contained in these asteroid classes.  We really only have good evidence on those classes that we think we have meteor samples of.  The rest would be guesses.