274 Sir C. L. GiesecJce^s Account of a Mimralogical [April, 



stone. I stopped for a night in a cabin, and made, on the fol- 

 lowing day, accompanied by some inhabitants of the island, a 

 pedestriaa excursion over the mountains, to the most western 

 point of it, called Achill Head, a distance of ten miles, where I 

 arrived late in the evening, and remained in the cabin of a water 

 guard. The following morning I went to the place described to 

 me, where the mineral, known here by the name of Achillstone, 

 is to be found. The substance so called is an amethyst-quartz 

 of different shades of colour, passing from amethyst-blue into 

 violet-blue and rose-red, and forms a vein of from one to two feet 

 broad, which is on its outgoing very much scattered and broken 

 into pieces. It runs in a southerly direction through mica-slate 

 of a coarse slaty undulated texture, which contains much quartz. 

 The amethyst bordering the matrix is in bacillar and cuneiform 

 district concretions, which terminate in six-sided pyramids. In 

 some places are found broken particles of rock crystal and com- 

 mon quartz of a greyish-brown tinge. At the foot of the moun- 

 tain a very coarse granular iron-shot quartz conglomerate, mixed 

 with brown common jasper and hornstone, covers part of the 

 mica-slate, which is converted into a grey greasy earthy sub- 

 stance, not unlike to powdered graphite. I could not trace any 

 other metallic substance on the spot except copper-pyrites, dis- 

 seminated in common quartz. 



Having now been nine weeks on my tour, and having latterly 

 been exposed to a good deal of fatigue, and the weather having 

 broke, I was reluctantly compelled to relinquish my examination 

 of the remainder of this interesting country. 



To this I annex a descriptive catalogue of the specimens, 105 

 in number, which I obtained on my journey, and which I propose 

 should form a part of the new Irish collection. 



A Descriptive Catalogue of the Mineral Substances found in the 

 Counties of Galivay and Mayo. 



County of Galivay. 

 No. 

 1 — 2. Quartz conglomerate, of rose-red and blood-red colour, 



with hornstone, from Woodford. 

 3 — 4. Dark leek-green jasper, from the same place. 

 4 — 6. Mica-slate, approaching to avanturine, from ditto. 

 7 — 10. Bog iron-ore (meadow iron-ore, James jn), of a blackish 

 and yellowish-brown colour, from a place near 

 Woodford. 

 11 — 12. Black turf, approaching to moor coal, covering the bog 



iron-ore. 

 13 — 14. Pearl-grey limestone, from Marble Hill. 

 16—18. Dark velvet-black limestone, with fragments of shells, 



