Spicular Calcareous Spar in Chalk Enlarge
June 1. 1812 published by Jas Sowerby London.
British Mineralogy
Calx carbonata

Spicular Calcareous Spar in Chalk

  • Div. 2. Imitative.
  • Var. spicular.

Crystallized Carbonate of Lime is very common, but I do not know that it has been mentioned in any work as occurring in Chalk. I therefore, while it elucidates this sort of spiculæ, figure it as of rare occurrence. It is from the Sussex lower or Hard Chalk, as it is often called. The spiculae are in general pretty uniform and very sharp, being very much elongated rhombs. I saw some approach to this in what was called the Hard Chalk about a mile S. E. of Newport* in the Isle of Wight in something like stalactitic exudations, if I may so call them. This stratum seems to join itself to the Limestones of the later formation, but not so gradually as I he mixing of Limestone in veins through some of the Chalk at Godstone. See tab, 7. Distinct Limestone at most quarries produces stalactites by means of the water running through it, such as Portland, Bath, Oxfordshire, &c. See tab, 6. and the Lime in the mortar of cellars or under some arches, as at Somerset House; yet it seldom approaches to crystallization, and Chalk appears less able to support crystallization.

This specimen was presented to me by Lady Wilson.

  • * A specimen of this, which I brought from the place myself, contained a perfectly round ball of Flint.
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