Square IPO sets off strong trading after company sputters at the starting block

Stock opens at $9, less than CEO Jack Dorsey had hoped for, but rises to over $12 in early trading to keep hope alive for so-called unicorn startups

The "unicorns" are still alive! Just. The share sale of mobile payment company Square got off to a good start on Thursday - but only after the Silicon Valley startup was forced to slash the price of its offer.

Square, one of the Silicon Valley "unicorn" startups - companies valued at billions of dollars despite an absence of profits - began trading on Thursday morning on the New York stock exchange.