Crystal Oscillator design with no data sheet
Chances are pretty good that a "50MHz" crystal is actually a 3rd overtone crystal, and if you make a simple Pierce oscillator (eg. with a 74HCU04) it will oscillate at 16.6667 MHz. If you only want it to oscillate at some frequency, not 50.000 MHz, then you can use the common circuit (load capacitors, some M ohm bias resistor, 1/6 of an unbuffered gate). 

To get the 50MHz, something like this should work, if it's a 3rd overtone crystal:



You will want to reduce the inductance to more like 8 turns, some experimentation may be required. Circuit is from here.