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Image of the day – 171
What’s in an image? Sometimes quite a lot, more than meets the eye. I’m posting an image every few days.
There’s a long stretch of dry stone Cotswold wall along the western edge of the Gloucester Road between Cirencester and Stratton. Walking along the footpath one day I was surprised to see the crystalline inclusions featured in this photo. The crystals look to me like a form of quartz (six-sided columns with six-faced prisms at both ends).
This might be part of a geode fractured open while quarrying the stone. There’s a small chance that the other side of the geode exists elsewhere in the same wall or in some other structure built around the same time. It seems that quartz geodes are not unusual in Oolitic limestone deposits. When they are stained purple purple the crystals are known as amethyst. The formation in the photo shows no hint of colour at all. The deposit must have formed from a particularly pure solution of quartz.
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