What is pitchblende primarily known for?

Pitchblende is primarily known as an important ore of uranium. It is a mineral that contains a high concentration of uranium, which is critical for nuclear power generation and the production of nuclear weapons. The significance of pitchblende lies in its role as a primary source of uranium extraction. The uranium mined from pitchblende is processed for various applications, including energy production in nuclear reactors and for scientific research.

The other options, while interesting, do not relate to pitchblende’s composition or uses. It is not a rare gemstone, nor is it a fuel source for aviation, which typically involves hydrocarbons or biofuels rather than uranium. Additionally, pitchblende is not a synthetic polymer; it is a naturally occurring mineral. This understanding highlights pitchblende's essential role in the context of uranium mining and contributions to energy needs and scientific advancements.