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.

Corundum crystals from Southern California

The mineral corundum, which is second only to diamond in terms of hardness, consists of aluminum oxide (Al2O3). Corundum comes in a variety of colors, depending on the trace amounts of other minerals (e.g., rutile = titanium oxide) it contains.

The color can be red, blue, yellow, brown, green, or purple to violet, and some crystals contain color zones. Pure corundum is white. If the color of corundum is red, it is called ruby. If the color is blue, it is called sapphire.

A friend recently gave me some corundum crystals from Cascade Canyon, San Gabriel Mountains, about 2 miles southwest of Mount Baldy, which is near the town of Upland in Los Angeles County, Southern California. 

A hand specimen (4 cm wide) containing small, scattered
 crystals of corundum. The color is between ruby and sapphire.
Most collectors would most likely refer to these crystals as ruby.

Close-up of the left-middle side of the hand specimen shown above.
The lenticular crystal in the lower right side is 4 mm long.

The corundum at the Cascade Canyon locality formed when complexly deformed sedimentary rock (of Paleozoic age) was contact metamorphosed (heated up) by small granitic intrusions (of Cretaceous age). 

If you want to see outcrop pictures and more information about this locality, just Google the phrase:  Cascade Canyon ruby