Wednesday, June 17, 2015

Jasperized (red) horn coral

Some of the most eye-catching fossils I have ever seen are the blood-red solitary rugose corals (horn corals) belonging to genus Lophophyllidium of Pennsylvanian age (approx. 308 m.y. old) from a locale in the Morgan Formation in the Wasatch Mountains, east of Salt Lake City, Utah. Many of these horn corals from this locality have had their calcareous exoskeletons replaced, in part or nearly completely, by jasper. Thus these fossils are commonly referred to as “jasperized horn corals.” Another common moniker is “agatized corals.” These specimens are coveted by collectors and especially those who make jewelry.

Lophophyllidium sp., Pennsylvanian, Utah,
8.5 cm length, 4.5 cm width.

6 cm length, 4 cm width.
Top view of specimen shown to the left;
width 4 cm.

Jaspar is an opaque, impure variety of silica consisting of an aggregate of microquartz and/or chalcedony. Jasper is commonly red (due to iron inclusions), but it can be brown, green, yellow, and rarely blue.

A nugget of jasper, length 5 cm.

1 comment:

  1. Great post, sample and photographs Dr. Squires, I was able to collect a rugose coral fossil during summer field.