Lamorna or Lands End granite comes from 3 quarries past Penzance in Cornwall, a few miles before the Lands End and on the ‘Land’s End pluton’ or igneous intrusion that gave rise to granite. It is classified, apparently as a ” … typical Cornubian abundantly megacrystic biotite granite.” [ 1 ] Ruth Siddel states ” Land’s End Granite from the Lamorna Quarries, like most of the stone extracted from the Land’s End Pluton, characteristically contains megacrysts of white feldspar, often >10 cm in length and up to 20 cm. These are set in a brown, quartz-rich matrix. Such granites are only encountered in the Land’s End and St Austell Plutons” [2 ]
The 3 quarry sites are Lamorna Cove, Sheffield and Castellack.
It’s said that in London Lamorna granite was used in the building of the Embankment in London, the bases of New Scotland Yard (the old one) aka the Norman Shaw Buildings, County Hall and various 19thC bank buildings in the City being shipped to London from the cove.  Sue Littledale states re it’s use in the Embankment – “The materials used to construct the embankment walls were of the highest quality. Newly patented Portland cement, the strongest available, reached from 6 to 14 feet below the low-water mark and was topped by massive blocks of granite. This granite, again the strongest Bazalgette could find, was loaded on to barges and brought up the English Channel from Lamorna Cove in Cornwall” 
Lamorna Cove is a typically stunning cove, with, apparently, the most photographed house in Britain! But I doubt that people know the history of the the abandoned quarry lurking above it. The quarries, there was a smaller one past the harbour, operated from 1848 to 1912 and while access is possible to the top of the spoilt heaps giving a lovely view of the cove, I couldn’t, in the scratchy brackeny, brambly height of summer find a way into the quarry itself.
The Illustrated London news of March 8th 1873 describes Lamorna Cove as ” Halfway between Penzance and the Land‟s End, along the south coast of Cornwall, and not far from the little seaport village of Mousehole, frequented by the fishers of pilchards and mackerel, is the picturesque valley of Lamorna. This place not only deserves its romantic name, but is entitled to historical fame. It was here, nine centuries and a half ago, that King Athelstan of the West Saxons finally defeated the ancient Celtic nation of West Britain. The site of his victory is marked by two lofty pillars of granite, erected at Bolleit, which means “the abode of slaughter.” ” [ 5 ]
The second Lamorna quarry is at Sheffield, yes Sheffield, a tiny village with a vast inaccessible quarry but you can see the massive pond clearly from above, with sheer cliffs dropping into the water. With the flooded quarries it is not always know now how deep they were and this could go down many 10s of metres as many do. It was operating till the 1980s apparently.
The 3rd quarry site is at Castelleck, no more than a hamlet now, with 2 small quarries of Lamorna granite both long closed and hidden away by bramble, goat willow and bracken. I got soaked and mightily scratched getting into it it, but it’s a beautiful sight!
 Siddall, R. & Clements, D., 2015, Never in the field of urban geology have so many granites been looked at by so few! A stroll along the Victoria Embankment from Charing Cross to Westminster & Blackfriars Bridge., Urban Geology in London No. 21, http://www.ucl.ac.uk/~ucfbrxs/Homepage/walks/Embankment.pdf
 The Geology of the building and decorative stones of Cornwall – Supplementary Publication – Granites and Elvans – Colin Bristow