Classic Horse Tooth growth Siderite from Wheal Maudlin, now in Lostwithiel Parish, Cornwall. Crystals of Siderite measuring to 0.9cm across the pinacoid display the characteristic growth zoning. Sides of the crystals show a segmented habit due to oscillatory growth, associated with colourless to translucent white Quartz crystals. A neat specimen from this singular occurrence at Wheal Maudlin.