Catchwords:

CONTRACTS — construction — where agreement to pay royalty following “actual sale” of mineral — where royalty a percentage of “net sales realisation” amount — whether “actual sale” occurs when title passes to buyer — whether “net sales realisation” is after deduction of sales realisation expenses

CONTRACTS — termination — where breach of time stipulation for making of payment — where demand made after giving further time for payment — whether breach of essential term justifying termination — whether repudiatory conduct evincing an unwillingness to render substantial performance