Scientists in Aberdeen have released pictures of volcanic glass particles from Iceland which fell in the city.
The images show the jagged edges of the particles, which were taken from the windscreen of a clean car parked at the James Hutton Institute.
They were collected on Tuesday - the same day Ryanair boss Michael O'Leary described the ash cloud as "mythical".
Flights were grounded on Tuesday and Wednesday when ash from the Grimsvotn volcano drifted into Scottish airspace.
The largest of the particles is 0.03mm across, with the smallest just 0.002mm wide. The images were taken using a scanning electron microscope.
Scientists at the institute said their composition showed that they did not come from last year's volcanic eruption in Iceland.
But they added they had not yet been compared with samples from the Grimsvotn eruption.
The ash cloud resulted in about 500 flights being cancelled across Europe after parts of British airspace were closed.
One of the worst hit countries was Scotland which saw flights at its main airports cancelled and hundreds of passengers stranded.
On Tuesday, Ryanair said it had flown over Scotland and challenged a ruling some flights should be grounded.
It said its 90-minute flight at 41,000ft showed there was "no visible volcanic ash cloud or evidence of ash on the airframe, wings or engines".
However, the CAA said the flight had not entered the so-called red zone.
Recent Met Office forecasts have shown that high density volcanic ash is no longer an immediate threat over the UK.
And Scottish transport minister Keith Brown has said bank holiday travel in Scotland was unlikely to be disrupted.
The James Hutton Institute was formed by bringing together the Macaulay Land Use Research Institute and Scottish Crop Research Centre.