Haketaka,
Have you seen the Co's presentation in August?
If you haven't I suggest you read it . If you have you will note that pages 14 and 15 disclose that in excess of 1.5 m ozs were produced between 1931 and 1950 exclusively from sulphide ores, and a similar amount from sulphide ore between 1984 and 2013.
I understand that the technology of extraction has improved very substantially in recent years.
This may persuade you to a different view.
BLK Price at posting:
70.0¢ Sentiment: Buy Disclosure: Held