Are these cards contradictory? No, they are not. Sage's Aquamarine's effect is the following:
Its owner will have many intelligent friends and keep those friendships for their entire lives.
while Lonely Sapphire's effect is stated as follows:
The owner of this sapphire will acquire vast wealth, but in exchange will spend a lifetime alone, forsaken by friends, family, and significant others
From what I understand here, a contradiction would occur if two things are polar inverses of each other. For it to be contradictory, Sage's Aquamarine must have an effect that, instead of acquiring vast wealth, will place you in a huge debt or anything opposite of 'acquiring vast wealth'.
What would happen if you used both cards? Sage's Aquamarine will grant him/her friends 'rich in intelligence' that will get him/her through life. Lonely Sapphire, however, will contradict this effect but in addition, will grant him/her a life of wealth.