Which type of jade was used by many of the ancient Mesoamerican cultures? Explain why this type of jade is unique when compared with other gems. What event in recent history changed geologist’s ideas about where the Mayans and earlier people found the jade they used in their artwork? (Site 1)

The quote below is an excerpt from the charter of the united nations: "the purposes of the united nations are: to maintain international peace and security, and to that end: to take effective collective measures for the prevention and removal of threats to the peace, and for the suppression of acts of aggression or other breaches of the peace, and to bring about by peaceful means, and in conformity with the principles of justice and international law, adjustment or settlement of international disputes or situations which might lead to a breach of the peace . " source:this section implies that the united nations is prepared to do what to keep world peace?