Rob Ixer points to the Altar Stone. 

Photo Copyright Phil Harding  

Tom has a hunch that the Altar Stone was gifted by the Orcadians to the Stonehenge project some 5000 years ago. 

The Altar Stone is a micaceous fine grained Devonian Sandstone.  Rob Ixer has looked closely at the minerology of the Senni sandstones and has determined the Altar Stone has come from a greater distance away from Stonehenge.  The blocks found intertidally in Westray Orkney some 650 miles away from Salisbury Plain seem to be a better candidate. 

Both the Senni sandstones and the Westray flagstones have fossils on their upper surfaces .  However the patterning of the fossils, the grain size and colour of blocks found in Westray and Papa Westray seem a better match to the Altar Stone.   

The Newgrange entrance stone has raised edges to the lozenge design, just like the fossil design seen above on the Westray stone. 

Patterning on Westray flagstones.   Note that the patterns are very similar to the Lozenge motifs carved on the entrance stone at Newgrange . 

Altar Stone swirl pattern ​

The top of the Altar Stone has swirl patterns and small fish debris. Match the species of fish and it would prove which formation the sandstone is from. 

Photo  English Heritage.