Perhaps no place in Ireland seems closer to the dark Celtic Otherworld than “Spink-ana-gaev"or Pinnacle Rock, a strange and eerie pile of boulders. “St Patrick’s Chair” is a massive block about 2 metres high, shaped like a chair and probably at least partly-artificial, sitting on a another large block amongst a dozen or more other blocks, one of which has a cup-mark and an unfinished cup-mark. Below the Chair is the well – in fact an open chamber above which is another massive boulder containing a fine bullaun 25 cms in diameter. It is said “never to run dry” – this is not surprising as the fern-covered site is like a miniature rain forest: every rock drips with water. A supporting boulder has a good cup-mark. Between the bullaun and the chair above are two Rag Trees, where some ‘offerings’ remain.
From Anthony Weir’s excellent ‘Irish Megaliths’ website.
irishmegaliths.org.uk/tyrone.htm
A little more detail from the NISMR:
“The chair faces S & is 1.7m high & 1.6m broad; the seat part is 0.75m high.
“The “well” consists of a large flat stone slab with a large bullaun & a possible smaller one on its upper face. There is a small cup mark carved on a supporting stone below. The large slab rests on several tumbled boulders. The bullaun is c.0.25m in diam. & 0.1m deep.”