Purple twinned Fluorite crystals to 8mm richly covering dark brown Siderite.  The fluorite is not the most lustrous but an interesting specimen none the less as it shows an early generation of large fluorite crystals overgrown by siderite and then the later generation of the smaller fluorite crystals.  Formerly in renowned welsh mineralogist John Mason's collection who sadly passed away a couple of years ago.  Those who have downloaded my lake district site guides will have noticed my referencing John's excellent published work.