This is an attractive and historic Siderite from the Tincroft Mine in Cornwall, probably from the mid to late 1800s. Cornwall was of course well-known for a variety of species and although Siderite isn't one of the common finds there it was always treasured by collectors in historic England, and this is extremely good even by modern taste of aesthetics! This is a special style, very rare, and once priced at more than their weight in gold if you look at old sales catalogues from the 1800s (see the book, Sparry Garniture). There are at least 2 dozen scintillating, green-brown, very well-formed, translucent Siderite crystals from 4 to 7mm in maximum dimension perched on milky Quartz with all of the Siderite crystals nicely isolated! In our opinion, there isn't a crystallized Siderite specimen this sharp, even featured in "The Minerals of Cornwall and Devon." Ex. John Albanese collection (1898-1969) with label. See more on Albanese at : https://mineralogicalrecord.com/labels.asp?page=2&colid=21
. Note that the Mineralogical Record archives confirm this label from 1953-1968. $15 was a lot more money in those days!