Ann: High Grade Discovery 4m @ 7.0% Cu - Exploration Update, page-200

There's no catalyst for this except for the last announcement addressing corporate activities between CNB and HMX. We have had some of the highest single day volume in quite some time so the most likely reason is one of the larger holders have liquidated their position and potentially taken a loss, driving down the share price. The good news is, that the holders on here are quite attentive and when published, you can check the full breakdown of top 20 movements from the last report to verify if this was the cause and by who.