We present QUANTA, an open-source blockchain built exclusively on NIST-standardized post-quantum cryptography: Falcon-512 (FIPS 206) for transaction signatures and Kyber-1024 (ML-KEM, FIPS 203) for node-to-node key encapsulation. No classical primitive appears in the critical path. The paper describes a protocol hardening framework for Falcon-512 in consensus, a parallel and cached block validation engine, integer-only consensus arithmetic for cross-architecture determinism, a compressed storage architecture, and a crypto-agility mechanism for future algorithm migration without a hard fork. Source code and Docker testnet image are publicly available.