Photo #124
Spider Black Pastel with some clean Chalcedony.
The stones pictured sort of look like glass, and while they are both mainly composed of Silica, unlike glass: chalcedony is composed of microscopic interlocking crystals (which gives it epic durability).
Chalcedony is a broad term that is used for materials that contain microcrystalline quartz. It is one of those terms that says 'Yeah, I sorta know what this is, but, I'm not going to pretend to be specific'.
Chalcedony often has material embedded in the matrix. Upcoming photos #126, and #129 are chalcedony with inclusions.
Fun fact: There is a decorative type of glass known as Chalcedony-glass, it was invented in Venice, Italy in the 15th century and used metal additives to the glass to imitate chalcedony colors. It was popular for a few centuries and then the technique was lost/forgotten. Of note: the techniques used to create Chalcedony glass at the time exposed the user to highly toxic chemicals including mercury vapor and arsenic and it would not be unreasonable to assume this is why it was discontinued. The technique of creating Chalcedony glass using a special metallic paste would be re-invented in the late 1800's with 'somewhat' greater care taken in its formulation.
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