I'm trying to identify a 1950's (NB: 1970 as it turns out) "pulp" sci-fi novel I read long ago. The cold war is still happening in its timeline. A very rare mineral is discovered that makes an FTL engine possible. To get enough mineral for even one engine, a collosal manhattan-project like effort was undertaken to isolate it but yielded only one gram; barely enough to power a single engine. The Soviets, however, have access to skads of this mineral, but don't yet know its significance. A planet is discovered that shows the signature of having lots of this mineral, so the West sends its one FTL ship there, desperate to get more of the mineral before the Soviets discover the secret of using it.
The ship almost destroys itself crossing the light speed barrier, but manages to arrive. At the destination planet they discover aliens who are pacifists and refuse to give any mineral to the hero because it could be used for war. After an impassioned plea about the evils of the communists and how they will use it for war which could threaten the aliens, the aliens come up with a compromise. They send the hero back with a substance that can be used to neutralize the FTL mineral and render the Soviet's deposit inert. They also relent enough to give the hero one more gram of mineral so that the engine will be powerful enough to not destroy itself crossing the speed of light barrier.