Global demand for cryptocurrencies has plunged as the possible collapse of [China](/news/china/index.html) ‘s second biggest apartment developer, Evergrande, frightens investors. [Bitcoin](/news/bitcoin/index.html) , the benchmark blockchain denomination, plummeted overnight from $AUD64,700 to four-month low levels below $56,000. A glut of ‘ghost city’ apartment towers in China is stirring fears about major economic problems should the conglomerate collapse.…