More than 100 Mozambicans filed a case in London alleging “serious human rights abuses” at Gemfields Plc’s ruby mine in the southern African nation, according to their lawyers.  Leigh Day, the London-based law company, said its clients suffered abuses at the hands of security forces at the Montepuez Ruby Mine, where they were shot, beaten, humiliated, subjected to sexual abuse, unlawfully detained and forced to carry out menial labor.  The claimants include family members representing four people who were killed, the law firm in a statement Monday.  Gemfields said in a statement that it denounces any form of violence or abuse and that it would “vigorously defend” itself against the claim.