As a point of interest, two of the three mining terms that definitions were sought for, albeit coal mining terminology, were in slightly similar use in the Derbyshire lead field.

SKIRTS  - (1) The extreme parts of the vein, the edges.  (2) Minerals lying between the ore and the rock [ref. Derbyshire Lead Mining Glossary by Nellie Kirkham CRG 1949 p.26]; 

and Dr. J. H. Rieuwerts in his book "Glossary of Derbyshire Lead Mining Terms" PDMHS 1998 pp 136-137 gives greater detail:-  

SKIRTS [see also CHEEKS, OUGES, TORRS, WOUGHS].   (i) In the more general sense the word referred to the walls of any type of lead vein.   Ealier usage was more precise Hopkinson {1644} appears to distinquish between the walls of a rake and those of a pipe:  "A Rake --- is Contained Between and Limited by two Woaghes or Woages --- a Certain firm and intire Rock, Torr or Hardness.   A Pipe is a Vein of Lead ore incompassed with a Lidstone or Roof, two skirts and a soul or Harthstone".   This definition is corroborated in a document relating to Hardinges Founder and Whitefield Vein, Middleton by Youlegreave, where it was stated that meers were set out:  "between skirt and skirt in every pipe worke and wough and wough in every rake worke" February, 1667 [PRO,DL 1/416].  (ii) Hooson [1747] gave a slightly different meaning stating the skirt to be mineral lying between the ore and the rock. (page 136)

SKIRT, NETHER SKIRT, UPPER SKIRT (see also HADING DIDE, HANGING SIDE).   A document relating to a dispute at Nestus Mine in 1676 gives much detail about the nature of the walls of the vein and pipe [DRO, GELL 31/88].   There are references to the upper skirt and the nether skirt, prsumably these terms must equate to the hanging wall and foot wall. (page 137).

SKIRTS DROP'T DOWN.   A phrase found only in Farey [1811], but presumably derived from the miners.   He refers to it only in his list of mines and there only at Ranter Mine and Yield Mine.   The context implies displacement of the vein walls;  certainly the Rantor Vein occupies a fault zone with one wall in shale and one wall in limestone in the upper limits [Rieuwerts, 1981].  (page 137).

SKIRTING THE LIMESTONE.   Driving a gate, level or sough on the interface of the limestone and shale, as at Stoke Sough in the 1760's.   The technique was utilised for ease of excavation in the shale, yet being able to observe any mineralisation in the underlying limestone:  "They have at Stoke Sough been skirting the limestone in order to relieve the veins watered and to make new discoveries near 300 yards of which has cost, cutting 15/- a yard" 1761-62 [SCL,OD 1161]. (page 137).

OUTSTOKE was not used as such but Jim Rieuwerts includes OUTFLIER in his book:  OUTFLIER.   A scrin or leading breaking out of a large vein.   The terms seems to have been used only during the 19th century and was confined to the Bradwell mines and in particular those on Moss Rake:  "Gave William and George Middleton possession of 8 meers and 6 yards --- in an outflier out of the Moss Rake Great Vein --- from a stake put down by the proprietors of the Reddlepitts Mine" 1st May, 1849 [Chats. Bar. Coll].   Green [1887] refers to "a flier from the vein (Moss Rake) above Outland Head".

Margaret Howard