Complex sentence: This trade continued until the 1962 military coup which nationalized the economy and declared all gemological resources to be the property of the Myanmar state and private transactions involving such resources was considered to be illegal, virtually halting the maritime gem export route.
Split into simpler sentences: This trade continued until the 1962 military coup in Burma which nationalized the economy, and declared all gemological resources to be the property of the Myanmar state. Private transactions involving gems were considered to be illegal, virtually shutting down the maritime gem export route.