Punchbowl

'The widespread Celtic faith in the magical powers contained in white quartz and rock crystal appears to extend at least as far back in time as the early bronze age, beliefs still held by people today. The presence of white quartz in Celtic sacred wells is so widespread as to prove that this rock was deemed worthy of giving as a votive offering to the gods. Particularly large quantities of white quartz were found in the sacred well at Ffynon Degla. Some stone circles have boulders of white quartz at their centre.'

"Stone circles....may have quartz boulders at the centre. White quartz is an indicator of copper, and may also have had a magical significance: its presence at monuments stretches from Neolithic right down to Early Christian times." from 'Early Ireland;- A Field Guide'

The use of white quartz in monuments and sacred sites extends from the Neolithic Age to early Christian times. 

The Celts regarded all their sacred places, wells, springs, pools etc. as gateways to the Otherworld.

"Alwyn Rees said the popular Celtic belief in the magical potency of white quartz and rock crystal 'appears to date back at least to bronze age times.'"  from the coming of the saints

It is probably worth quoting again here what Chanter wrote in his handbook

p.13.- 'In traversing the Island the visitor is struck by the white glittering appearance of the ground, it being thinly covered in many places with white gravel, composed of cubes or nodules of quartz set free by the decomposition of the granite.'

In view of the above, the following quote from ( chanter, again ) makes interesting reading;-

"Mr Gosse also describes another very curious object whose origin and use may possibly date back to the very same early period "Lying on the side of a valley, which takes its name from the object itself, the Punchbowl Valley (through which runs a little brook, which originates near the middle of the island, forming there a small lake or pond) is a basin of solid granite four feet in diameter and one in depth, with a uniform thickness of six inches. Both the concave and convex surfaces are segments of very perfect spheres, and the whole conformation is so regular as scarcely to admit a doubt that it is the work of art: and yet when we enquire what could be the purpose of such a piece of sculpture, or how it could have got to a situation so wild - so remote from any trace of man - and altogether so unlikely as the side of this boggy valley, especially considering that its weight alone must have presented no small obstacle to its removal from any other locality, we know not what answer can be returned."

The writer then mentions, but without attaching any significance to the observation, the " disintegrated nodules of quartz lying loosely in the concavity." Mr. Gosse visited Lundy sometime around 1851.

The description of the 'Punchbowl' on Lundy seems to depict a type of object frequently found in Ireland ; a 'Bullaun', 'Turning-stone' or 'cursing stone.' These are hemispherical depressions in rocks or boulders (frequently quartz conglomerates). They are usually found associated with early christian sites, but most authorities agree that the Bullauns pre-date the christianization of the sites and that they served some ritual function.

 "Turning-stones, or 'cursing stones' are also associated with bullauns; hemispherical depressions in boulders or rock (often quartz- conglomerate), as much as 50cm. in diameter and half as deep. Bullauns may be single, double or multiple, and are most usually associated with Early Christian sites. They are very common in the midlands (Ireland)(where of course the very soft limestone is as easily hollowed by hand of man as by natural means). It has been suggested that they were communal grinding mills, even though more efficient querns were used during the Iron Age, and it is also highly unlikely that the bullauns at Glendalough or Clonmacnois could have ground enough grain for the large monasteries there. It seems more possible, however, that they were used to grind special ritual food in pre-christian times, and were later christianised. The eating of ritual grains in the form of gruel is well known in pre-christian Europe, and in Ireland they may well have been ground in bullauns. In Christian times medicinal herbs would certainly have been prepared on monastic sites, and bullauns would have served the purpose admirably." from 'Early Ireland;- A Field Guide'