cf. mu 1150, with a different spelling; see also mu 1144.
Considered as a weight (it could also be a sum of money, as perhaps in the second quotation) the mina -- more exactly, mna -- varied from place to place. On the widespread Attic-Euboic standard it was just short of an imperial pound, or c.437 grams, but other systems had a rather lighter mina; and the stones or bullets archaeologically preserved (see Pritchett, below in n.1) are considerably lighter than this.
[1] Adler makes no comment on the source of this statement, but it is surely Diodorus Siculus 19.109.1-2, on the Balearic slingers used by Hamilcar against Agathocles in 311 BCE; they "are accustomed to throw stones weighing a mina". For the Balearic Islands (present-day Mallorca etc.) see generally OCD4 p.222. For Balearic slingers cf. beta 83 and sigma 1728, and see generally on slingers OCD4 p.1376; Pritchett 1-65. Stones "weighing a mina" seem to have been in plentiful natural supply: cf. Xenophon, Art of Horsemanship 4.4, and Cavalry Commander 1.16.
[2] Or perhaps a mina-weight of clay, to make pottery to carry it in? At any rate, both quotation and subject are unidentifiable.