Three men threatened staff with knives and swords, and smashed open display cases at the Hamilton & Inches store in George Street, Edinburgh at around 11.30am yesterday.
They made their escape in a white BMW car, driven by a fourth man, which was seen to drive east along George Street, down Howe Street and along Heriot Row.
The car was recovered by police a short time later and is currently being forensically examined.
Police initially appeal for any witnesses yesterday but did not put a value on the stolen goods. A force spokesman said today that a full inventory of the stolen items is being carried out and it is estimated that over £1 million of valuables were taken.
Detective Inspector Craig Finnie said: "Staff were left extremely shaken and a major investigation is under way to trace those responsible.'
"While we remain keen to speak with witnesses who were in the George Street area at the time of the robbery, we also wish to trace anyone who remembers seeing both getaway vehicles in the Gloucester Lane area before or after the crime was committed.
"Furthermore, anyone with any further information relevant to this inquiry is also asked to contact police immediately."
A statement on the Hamilton & Inches website said: "I am pleased to say that all of our staff are okay.
''We will however be closed for business in order to make our showroom safe.
''Please be assured that all of our customers' jewellery is held safely in our vaults and is untouched.''
Robert Kirk Inches and his uncle James Hamilton opened their first premises at 90A Princes Street, under the name Hamilton & Inches on November 10, 1866.