Ruby hunting for the Kid's Challenge Program

Recently, the Mineral Science staff was contacted by the executive producer of the Kid's Science Challenge, Jim Metzner. Jim was looking for geoscientists, researchers, and specialists in the field of geology to produce a kid-friendly program on the topic. Alyssa Morgan and I got interviewed by Jim at the Museum, and we also did a fun field trip to collect rubies in Cascade Canyon, near Mt Baldy, only an hour away from Los Angeles. As Alyssa already wrote a blog post about the geology of the deposit (here), I'm reporting here just a photo album of our field trip.

 Our group getting ready to hike across bushes and rivers.

 The valley in which we will find the ruby-bearing rocks.

 On our way to the outcrop, the first part of the trail is magical.

 Enjoying a bit of shade.

 The hike really begins when there are fallen trees to climb over and poison oak to avoid.

 Danger: poison oak next to the fallen tree!

 A beautiful boulder of gneiss showing flux features with white veins showing boudinage.

 Just before the outcrop, a last obstacle: the river to cross. We were lucky, there was not much water in San Antonio Creek.

 The outcrop is not bedrock. We are actually looking through a landslide deposit. The outcrop itself is almost at the top of the mountain, but luckily for us, the landslide moved the ruby-bearing rock down the hill.

The rubies are found in an aluminum-rich metamorphic rock, most likely a gneiss representing the ancient ocean sediment.

A close-up on the same rock with the elongated pinkish prism of ruby.

I extracted a group of ruby crystals out of the rock, which looked good...

... until I found this better one!

After 30 minutes of searching in the same area, each member of the group began to collect on its own, finding great specimens.

Alyssa got a good one on matrix.

And here is a good one I extracted from the matrix: view of the hexagonal base.

View from the side of the elongated prism.

Alyssa getting interviewed by Jim about the geology of the area.

The program will be find a few months from now on the Kid's Science Challenge channel.

Jim Metzner also recorded some sounds for his radio program Pulse of the Planet.

Some more rubies extracted from the matrix.

More sound recording by Jim while the rest of the crew is still ruby hunting.

Nice view of the creek just by the ruby outcrop.

Meditation by the water.

View of the river.

And everybody is ready to go... that means crossing the river again!

And finding our way back through the bushes. 

I just loved this odd looking rock that was scattered along the boulders of gneiss. Meanwhile, people are climbing fallen trees again!

My favorite shaded area!  Must have been a cabin there a long time ago.

Back to the main trail, not far away from our cars, our trip is almost over.

But there is no good field trip without good food at the end! Pizza from Zelo Pizzeria in Arcadia!

Thanks again to the Kid's Science Challenge team for involving the Natural History Museum of Los Angeles County in their program!

Cascade Canyon Field Trip

The geology of Southern CA can get very complicated very quickly.  Most of Los Angeles lies in a large deep ocean basin. For the last few million years this basin has been rising due to compression between the Pacific and North American plates (we are right on the plate boundary a.k.a the San Andreas Fault).  So most of the rocks around us are Cenozoic ocean sediments (such as mudstones/shales) full of fossil sea creatures and oil!  The San Gabriel Mountains (and all the mountains bordering our basin) are a different story, they contains blocks of land that are much older.  They are bits of islands or continent fragments that crashed into the western edge of North America as the Farallon plate was subducting underneath.  Long story short, some of the rocks in the mountains formed over 1-2 billion years ago during times when the continents were in completely different places than they are now.  Instead of the layers of young ocean sediments of the basin, they contain a wide variety of igneous and metaphorphic rocks that are not necessarily related to each other than that they have been smashed together!

One old rock of particular interest to mineral collectors is a gneiss near Ontario Peak.  This metamorphic block also contains beds of marble with pyrite and lazurite (Lapis Lazuli - very rare and difficult to find).  The gneiss is most likely a metamorphosed ocean sediment as it contains a good amount of aluminum (Al) and carbon.  The aluminum comes from clay minerals, so "muds" often have aluminum, not enough to mine Al metal, but enough to make Al rich minerals like corundum (Al2O3).  Corundum won't grow until a certain high pressure has been reached.  At lower pressures, Al rich minerals like micas will grow first.

Corundum is a popular mineral!  When it is vivid red we call it ruby, any other color and it is sapphire.  The Cascade canyon corundum is a pretty pinkish-red, maybe a ruby, maybe not quite.  It is darkened by inclusions of graphite (C) and rutile (TiO2).  Most of the crystals are tiny but can reach up to an inch!  Dravite tourmaline can also be found in tiny gemmy yellow-green crystals.  Both of these minerals fluoresce vividly in UV light.

Some time ago a landslide moved much of the rock down into the canyon where is can still be collected along San Antonio creek.  Much of the collecting area is within the borders of the Angeles National Forest and collecting is illegal without a permit.  Collecting permit applications are available from the Forest Service.

The Gem and Mineral council recently had a field trip to collect the corundum.  Getting there is not easy!  It was almost 100 degrees and field trippers must hike down into the canyon and then fight through bushes and poison oak, climb over fallen logs and boulders!  Once at the creek, in the shade, collecting is very pleasant.

Click to read more about the field trip and Tony's helicopter search and rescue!