UBS joins Canaccord in downgrading GT; Rubicon also hit

• "We believe GT can still hit the midpoint of its sales guidance of $600-$800M but believe our checks of a slower ramp in 2Q14 makes the high end more challenging," writes UBS' Stephen Chin while downgrading GT Advanced (GTAT -13%) to Neutral.
• Chin is worried about the pace at which Apple-related sapphire output is growing, and has respectively cut his 2014 revenue and EPS forecasts by $100M and $0.05 to $700M and $0.12. Consensus is at $696.5M (+133% Y/Y) and $0.08.
• Canaccord's Jonathan Dosheimer, who this morning cut GT to Hold, expresses skepticism the iPhone 6 will use sapphire cover glass in large volumes, and considers 2016 EPS upside unlikely unless sapphire cover glass is used across Apple's iPhone/iWatch lineups.
• Dorsheimer's remarks follows a June report claiming only the 5.5" iPhone 6 will feature sapphire cover glass - the 4.7" model will use Gorilla Glass - and that the 5.5" model will be in short supply through year's end due to sapphire yield issues.
• Sapphire wafer vendor Rubicon (RBCN -5.9%) is following GT lower on a weak day for tech. GT is still up 95% YTD.