52 
CLAY IKON-STONES, 
534. ‘‘ Henry’s Pin.” I 
535. Stone Vein.” 
536. Upper Jack Vein.” 
537. ‘^Penydarren Jack Vein.” 
Shelf II. 
South Wales.— Central Anticlinal 
District. 
Series from Cwm Avon : — 
538. “ Black Band.” 
Cwm Avon (or Afon) Glamorgan¬ 
shire. 
539. “Big Mine.” 
540. “ Middle Big Mine.” 
541. “Balling Mine” (large 
course). 
542. “ Balling Mine ” (smalt 
course). 
Shelf III. 
Cwm Avon —continued ;— 
543. “ Sulphury Mine ” (top 
course). 
544. “ Sulphury Mine ” (middle 
course). 
545. “ Sulphury Mine ” (bottom 
course). 
546. “ Cefn glo Balls.” 
547. “Middle Clay Vein.’^ 
548. “Five Feet Pin” (top 
course). 
549. “ Five Feet Pin ” (bottom 
course). 
550. “Jack Mine.” 
551. Clay Ironstone from the 
bed considered to be the best in 
the ground worked for the furnaces 
at Maesteg Iron Works, Gla- 
7 norganshire. 
Presented by D. Smith. 
Shelf IV. 
South Wales.— Western or An¬ 
thracitic District. 
Seiies from Ystalyfera, near 
Swansea :— 
552 & 553. “ Black Band.” 
554 & 555. “ Black Pins.” 
556. “ Soap Vein.” 
Shelf V. 
Ystalyfera —continued :— 
557 & 557a. “ Penny-pieces. ” 
558 & 559. “White Pins” 
(sometimes called “ Coedfalda 
Mine”). 
560. “ Black Vein Mine.” 
Wall-case 53. 
Shelves I. & II. 
Ystalyfera —continued :— 
561 to 568. “ Little Vein 
Mine.” 
Ten courses in 18 feet ground. Yields 
7,000 tons per acre. This is the most 
important measure of ironstone in this 
district. 
569. Argillaceous Ironstone, 
near the bed called “ Sturdy 
Vein.” 
In the cracks of this ironstone brovn 
spar and quartz often occur. 
Shelf III. 
m 
Ystalyfera —continued :— 
570. “Billets.” 
571. “ Harnlo Mine.” 
572 to 574. “ Brass Vein.” 
575. Argillaceous Ironstone, 
the cracks of which are filled with 
Iron Py rites. 
576. “Little Brass Mine.” 
Ynis Cedwin. 
oil & 578. “Cwm-Fil Mine.” 
Ynis Cedwin. 
* See Vertical Section of Geological Survey, Sheet 3. 
