The Samarco tailings dam disaster in Brazil a massive human tragedy, and the cost is yet to be counted in both loss of life and financial consequences to joint venture miners BHP Billiton and Vale.  
For investors of BHP, known as The Big Australian, it is more bad news piled onto an already miserable year. On Friday the share price dipped briefly below $20 a share, a long way from the heady days of 2011 when the share price hit its peak of $46.30.
The share price of BHP Billiton is at its lowest since   November 2008, even including its recently spun-off South 32 business. Shares are now down 33 per cent from their high this year of $31.89 in   March. So what's behind the fall? 

Commodity prices driving share price action....
Iron ore is the cornerstone of BHP's business, and iron ore has been steadily declining this year, dipping to a six-year low. Investment banks including Goldman Sachs predict the bulk commodity will extend its declines into 2016, as miners continue their production despite weak demand growth from China as its economy transitions from being driven from manufacturing to consumption. A stronger US dollar as the US Federal Reserve raises interest rates will also keep a lid on demand. 
A report this week by commodity trader Noble Group warned steel output in China is set to tumble. 
This chart is what sets the diversified miner predominantly apart from its rival Rio Tinto. BHP Billiton has a substantial petroleum business and forecasters are reluctant to call a bottom, despite prices heading downwards to $US40 a barrel, with the Organisation of Petroleum Exporting Countries maintaining their robust supplies and Iran poised to ramp up production.

Copper copping it
Copper prices are also at global financial crisis lows, with investors fretting over the slowdown in China's economy and the impact of a stronger US dollar. 
"Macro sentiment is the main overlay at the moment ... that dollar strength and weaker Chinese data is hitting the market," London-based Citi analyst David Wilson told Bloomberg.

But... BHP's response has been to ramp up production
In   July the miner committed to cutting back supply in all but one of its four key pillar commodities: copper, petroleum and coal. But its iron ore business was ramping, as part of its longstanding commitment to run its expanded Pilbara production at its capacity. 
The ramp up comes amid a global glut in most commodities, which has in turn weighed on the Australian dollar, and a slowdown in Chinese manufacturing, which is Australia's biggest customer for iron ore. 
It is especially dark days if you are in noted economist Saul Eslake's camp, who said this week the last commodity boom in human history may have finished. 

Profits plunging...
BHP's underlying profit, plunged 53 per cent to $US6.4 billion this year, while its statutory profit, which includes writedowns and other one-offs, fell to $US1.9 billion, a staggering 86 per cent lower. 
Commonwealth Bank analyst Andrew Hines warned that if commodity prices stayed where they were through the 2016 financial year, BHP's net profit could fall to zero.

...sending dividend yields sky high
Yields of BHP are at "once in a lifetime" levels and most analysts are now questioning the ability of BHP to maintain its progressive dividend policy. The policy states the company will pay the same if not increase their payouts. But with its share price value falling, and the company's market cap collapsing from $250 billion in 2011 to $74 billion now, is is possible to keep this promise? 
Commonwealth Bank's Hines, the only analyst on Bloomberg who has a "sell" rating on the stock, said the miner would be forced to cut its dividend by as much as 35 per cent in the next two years.
"In our view, BHP is likely to decide that a strong balance sheet is more important that propping up an unsustainable dividend with debt," he said.
"We recently downgraded our FY17 dividend forecast to US80 cents per share (from US$1.24ps)."