Octaëdral Calcedony Enlarge
April 1 1809 Publish’d by Jas Sowerby London
British Mineralogy
Silex Quartzum, var.

Octaëdral Calcedony

  • Class 2. Earths.
  • Order 1. Homogeneous.
  • Gen. 4. Silex.
  • Spec. Quartzum.
  • Div. 2. Imitative.
  • Var. Octaëdral.
  • Syn. Quartz Agathe. Haüy, 2. 424.

I was favoured with this fine specimen by Lord Heathfield, who sent it from Beer Alstone in Devonshire. It is a secondary crystallization, having taken the form of some other substance that was prior to it. It has here taken the place of Fluor or Galæna, most probably Fluor somewhat like that of tab. 26. Some of the casts are extremely neat, others are somewhat hollow, and have Quartz crystals within them.

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