Thursday, February 23, 2017

Green fluorite

One of my more recent posts deals with a locality where corundum (sapphire, ruby) can be found in Southern California. This new post deals with another Southern California mineral locality, and it is where green fluorite can be found.

Flourite consists of calcium fluoride. It is a common mineral and used as an indicator of a hardness of 4 on the Moh’s Scale of hardness from 1 to 10. Flourite can come in a wide variety of colors (especially purple), but green fluorite is a relatively less common color.

The green-flourite locality is called the “Felix Mine” locality, which is just north of the city of Azusa, California in the foothills of the San Gabriel Mountains. The mine, established in 1892, is no longer accessible because of urban sprawl, and the vein which yielded the green fluorite has long been mined out. The specimen shown below was recently kindly donated to me by a collector.

Green fluorite (maximum dimension 2.3 cm) from the Felix Mine, Southern California.
The black material is the mineral galena (iron sulfide).

The largest crystals ever found of green fluorite at the Felix Mine were reportedly about 8 cm long. Most of the crystals, however, were very small to small size. The fluorite occurred in numerous subparallel veins cutting through decomposed granite. The mineral galena is commonly associated with the green fluorite.

Thursday, February 9, 2017

Trigonarca californica

This post concerns a common Late Cretaceous bivalve (clam) that lived in California approximately 92 million years ago (Turonian time). It is Trigonarca californica Packard, 1922, which is known from northern California (Siskiyou County) to southern California.

The specimens shown below are from the Santa Ana Mountains of Orange County, and they were collected from the Baker Canyon Member of the Ladd Formation. As this locale, where specimens can be abundant, this species lived in sandy, warm, shallow-marine waters. A collector recently kindly donated these specimens.

Right-hand valve of Trigonarca californcia Packard. Length 4.4 cm.

This unusual specimen shows the somewhat separated valves of a formerly closed-valved specimen
of Trigonarca californica Packard. The hinge with its distinctive teeth are nicely preserved. Length  of the left-hand valve (at the front of the photograph) is 4.3 cm.

The sturdy shell of this species has the shape of a rounded triangle. Its teeth (dentition) are distinctive and consist of numerous, relatively heavy, short, straight teeth along its hinge.

Genus Trigonarca, which belongs to family Glycymerididae, was widespread, with occurrences in North America, Europe, South Africa, and India. Trigonaraca is of Late Cretaceous age.