A Bit of Blue Gemstone for a Friday

As I've mentioned a few times, our new Science Community Center at Modesto Junior College is opening soon. Most of the first floor will be devoted to the vastly enlarged Great Valley Museum along with a planetarium and an observatory. One of the aspects of my involvement has been in developing an exhibit of California's state symbols. What today is a few pictures on a wall in the present museum will in a few weeks be a complete display with a full skeleton of a sabertooth cat (our state fossil), a gold specimen (our state mineral), a big chunk of beautifully glossy serpentine (our state rock; yes I know it's called serpentinite, but the legislature was unaware of this) and some of others like our state grass, bird, and flower.

Today I got to take a really close look at our state gemstone, which is one of the most obscure such designations in the United States! Can you say what this beautiful blue mineral is called?

The first Europeans to discover it thought it was sapphire. It's so rare that it was only described for the first time in 1907. And gem-quality specimens are found in abundance at only one mine in the entire world. It is a barium titanium silicate mineral called benitoite (after San Benito County, where it was found).

Benitoite crystallizes in the hexagonal crystal class, but forms a rare triangular type of crystal within the class. It is a beautiful blue color, but is a bit on the soft side (6-6.5) for extensive use in jewelry. It is also known for fluorescing in ultraviolet light. The matrix in which it is found is called natrolite, and sometimes elongated crystals of neptunite are associated with the benitoite.

It's a beautiful specimen that we'll have on display. Don't miss it if you are ever in Modesto!

Destroying Our Heritage: California Mining and Mineral Museum Raided

It makes me sick at heart...

A closeup of the Fricot Nugget

I just can't believe how low some people will go that they would destroy historical treasures that belong to all of us. I see the sickness in the wanton destruction of cliff dwellings and graves of our Native American ancestors by pothunters. I see it in the criminal who took a knife and killed an iconic Jeffrey Pine that once graced the summit of Sentinel Dome in Yosemite National Park. I see it in the destruction of entire forests by the sick action of arsonists. And now the sickness hits ever closer to home...

The 13.8 pound Fricot Nugget

We had one of the nicest mineral exhibits to be found anywhere, at the California Mining and Mineral Museum in Mariposa up in the Sierra Nevada foothills. It was a favorite stop during many of my field trips to the Mother Lode, and we just fought a long battle to prevent its closure by a financially strapped state government.

A large sample of benitoite (the state gemstone) and neptunite in matrix. These are found at a single locality in the Coast Ranges of California

On Friday, two thugs in black masks waving pick axes terrorized the museum volunteers, and broke into the exhibits, stealing numerous priceless gold and gem specimens. The stories on the theft mention a $2 million heist, but I do not know the origin of that number.

Benitoite, the California State gemstone

The robbery was nearly stymied by the security system, because when the thieves tried to hammer their way into the safe containing the Fricot Nugget (see the top two pictures), the system started to close the vault doors, almost trapping the thugs inside. I guess one of them wedged his body in the door and they escaped, taking what specimens they could grab. The area was flooded with law enforcement personnel in moments, but no arrests have been made yet. The Fricot Nugget was not taken (it was in a separate more heavily fortified vault).

Benitoite specimen

I have no inside information about what was taken, but I've been documenting the vault specimens for years on this blog. They include numerous beautiful crystalline gold samples as well as the more normal rounded nuggets.

Crystalline gold

What drives people to do such sick things? Yeah, greed, I know. I can't imagine how they could think they could sell these things in a pawnshop. These samples are famous enough that gold dealers  wouldn't touch them. Melting them down turns these samples from priceless to mere gold, and the actual poundage isn't that much: a few thousand dollars, maybe. All for a meth fix, I guess. Worthless human garbage.

More crystalline gold

I trust that the morons who did this thing would never read a blog like this, and I don't care. I just hope you brag to someone, that you try and sell these samples to a reputable dealer. Because I want to see your sorry worthless asses tossed in jail for a long time.

Isometric gold specimen

I am sorry if you never had a chance to see these beautiful specimens that graced the museum. I am sorry for the trauma suffered by the volunteers who were also victims in this crime. These people give of their time so the museum can stay open. I hope the stolen minerals can be returned to their rightful place so the experience of seeing these treasures can be shared by all.

Leaf gold from the now-closed Harvard Open Pit Mine

Here are a few examples of past blogs about the Fricot Nugget and other specimens at the Mineral Museum:
http://geotripper.blogspot.com/2010/07/other-california-ca-state-mineral.html, http://geotripper.blogspot.com/2008/03/beyond-dreams-of-avaricesierra-gold.html, http://geotripper.blogspot.com/2012/03/priceless-collection-of-minerals-to-see.html.

A Priceless Collection of Minerals: To see, or not to see

I was in the field yesterday with my students, and one of our stops was at the California State Mining and Mineral Museum in Mariposa at the south end of the California Mother Lode. I am offering up a selection of photos of some of the finest mineral specimens you will ever see anywhere, but I hope you will read to the end of this post as you look at them. Enjoy!

The first few images are some of the striking specimens of crystalline gold. Gold crystallizes in the isometric crystal system (three equal axes at ninety degrees), but the crystals themselves are rarely seen because gold is so malleable that the structure is lost the moment the mineral rolls in a stream.

Gold crystals, then, instead of gold nuggets. They are just gorgeous, and priceless, because the vast majority of crystal specimens were melted into bullion along with all the other gold during the gold rush days, even the biggest single nugget, one that weighed close to 200 pounds.

 You just don't expect gold to look like this.

Or this...when the Harvard open-pit mine was operating in the 1980's and was about to close down, the miners hit a rich pocket. Mine employees who had hardly ever seen even a small bit of gold in the disseminated ores were surprised to see a 60 pound chunk of gold pass by on the conveyor belt. It was composes of leaf gold, a crystalline variety composed of...um...leaf-like flakes of gold. The entire mass was preserved and can be seen at the Ironstone Winery at Murphys, but a large flake can be seen above.

And then there is the Fricot Nugget. The 13.6 pound nugget is the largest single gold mass preserved from the Gold Rush Days, having been discovered in 1865. It lay a long time in a safe deposit box, almost completely forgotten. It came to the state collection in 1943.

An exceedingly rare mineral is a beautiful blue sapphire-like gem called benitoite. It is found at a single mine in the California Coast Ranges. It was designated the California state gemstone in 1985.

The sample below includes two very rare minerals. The black mineral is neptunite, which is often found in association with the benitoite.

Another unique mineral assemblage in California comes from the pegmatite veins in San Diego and Riverside counties. These veins contain immense crystals of quartz, feldspar, muscovite mica, and a group of rare gemstones, most notably tourmaline. For a time in the early 1920's tourmaline was the most prized gem in China, and many incredible crystals were exported.

Other minerals came to the state from all over the world. Below is a striking example of beryl (aquamarine), a relative of emerald.

And sulfur crystals deposited on aragonite crystals...

And some beautiful crystallized azurite and malachite, ores of copper.

And opal from the Virgin Valley in Nevada...

Another example of pegmatite contains a form of feldspar called amazonite.

Some more spectacular azurite crystals.

The crystals below are wulfenite, an important ore of molybdenum and lead.

And finally, the museum has an excellent exhibit of meteorite specimens, including this cross-section of the crystallized elemental iron of the Giant Goose Meteorite, which fell in Modoc County in 1938. The original weighed over a ton.

Wouldn't you just love to see these incredible rare specimens for themselves? I can assure you that it is a great exhibit, quite worthy of a short diversion on your way to Yosemite National Park. But you don't get to see them. You may never get to see them ever again. Why? Because the California State Mining and Mineral Museum is on the state closure list, one of 70 parks to be closed and shuttered because of cuts of $22 million to the state park system, approximately 70 pennies for each inhabitant of the state. I am incensed that the people of our state legislature are so incredibly short-sighted as to allow this to happen.

I feel hopeless sometimes at the stupidity I see. State parks generate economic activity, they don't drain it. Closing these parks makes no sense at all. Mitchell Caverns has already closed, and vandals have already done grievous damage. It will cost so much more to re-open these parks once they have been degraded. And yet that is what our government has decided to do, come June. I don't quite know what would work to change this, but one can start by letting your legislators know how you feel about this. The parks have few friends in the legislature obviously, but the politicos might listen to someone besides their ever-present lobbyists if they heard from their constituents. Who knows? There is a facebook page for the California State Mines and Mineral Museum, and there is the California State Parks Foundation, the best place to get information on how to proceed politically.

I know that blogs are places for the writing of many words, but I have few enough words that can express my disgust at the members of the state legislature and government for allowing this to happen.

The Other California: The CA State Mineral Museum - this is art, darnit!

I know it when I see it. Purveyors of that which we would not call art would use shiny perfect minerals that would cause the viewer to objectify the image, and desire to possess it without appreciating or respecting the intrinsic value and quality of the mineral. I would never stoop that low just to get readership here at Geotripper. Just ignore the "xxx" and "big gold nuggets" in the blog tags. Besides, these things are in a museum. That makes this art, darnit!

And what a great museum it is! One would think that the official state mineral collection would be housed in the state capitol somewhere, or in San Francisco or Los Angeles. The collection actually was in San Francisco for many years, surviving the 1906 earthquake, but in 1983 the collection was moved to Mariposa in the Sierra Nevada Mother Lode, where it resides in the California State Mining and Mineral Museum, a unit of the state park system. The choice of Mariposa makes a certain amount of historical sense, as the town hosted one of the very first hardrock mines and mills during the Gold Rush, the Mariposa, discovered by Kit Carson and ultimately owned by John C. Fremont, two of the big players in early state history.

One of the premier attractions of the collection is the Fricot nugget (that's a part of it at the top of the page), the largest single remaining nugget from the Gold Rush days, at 13.8 pounds. It sits in a vault within a vault. Most large nuggets were simply melted down (there is a larger nugget at the Ironstone Winery, but it was found in the 1990's at the Harvard Mine). There is a facsimile of the biggest nugget ever found, which originally weighed in at around 200 pounds.

The other smaller gold sample shown above is extraordinary as it shows the crystalline nature of the metal. The mineral forms octahedral crystals, but they aren't seen often because the malleable metal gets pounded into the more familiar nugget shape while being rolled in a stream. Samples like this one have to come from the quartz veins in mines.

The museum has a spectacular collection of other minerals, including some of the best specimens of our state gemstone benitoite. This exceedingly rare sapphire-like crystal is found at a single locality in the world, a serpentine outcrop in the Coast Ranges of San Benito County.

The museum has a host of other minerals on display, like the malachite sample above, and the aquamarine sample below. There are some excellent interpretive exhibits regarding the history and current state of mining in California, and even a 175 foot long tunnel that recreates a gold mine.

Admission is $4.00, but they offer discounts for school field trips (call in advance). The staff and volunteers are knowledgeable and helpful. The museum is located on Highway 49 just south of the town of Mariposa at the county fairgrounds. Unfortunately, the museum has been one of the pawns in the state budget wars, and has been threatened with closure off and on. It could use some friends in the capitol...

The Other California is part of my continuing explorations of the California that you don't always find on the postcards.

The Other California: Geology and our State Symbols

Gold was the obvious choice for the state mineral of California, but at the time, no other state had actually selected a state mineral, or rock for that matter. California was the first in each category, making it official in 1965. More than 100 million ounces of gold was mined across the state beginning before 1800 and extending to the present day (some mines were in operation in the far south of the state, just over the border from Mexico in the late 1700's, but no rush occurred to speak of). A minor rush took place in 1842 in Placerita Canyon near Los Angeles, but the ores were soon exhausted. It was the discovery of some flakes in the millrace by James Marshall at John Sutter's sawmill at Coloma that led to the mass migration of hundreds of thousands of people looking for riches that forever changed the state (and sealed the fate of most of the native indigenous people who were already here). For better or worse, gold was central to the early history of the state.

At the same time that gold was selected as the state mineral, serpentine was designated the state rock. Serpentine (more properly called serpentinite) is a metamorphic rock derived primarily by the alteration of peridotite (a rock from deep in the earth's mantle composed of the gemstone peridot, also known as olivine). Chemically it is a magnesium silicate. It is a relatively common rock in California and relatively rare in most other places, and was picked for an ironic reason: it is a source of asbestos, which at the time was considered a valuable resource. The dangers of asbestos in building construction was not generally realized at the time.

For different reasons, I think serpentine was an excellent choice for our state rock. The fact that the source of the rock is deep in the earth's mantle, beneath the 15-25 mile thick crust, is a revelation and acknowledgement of the incredible forces that have shaped the state. Imagine what it takes to bring masses of rock from such great depths! California has the incredible scenery that it does because of forces of movements along plate boundaries, whether the lateral movements along the San Andreas fault, the vertical churning that occurs along convergent boundaries, where ocean crust is driven underneath the edge of the continent, or the splitting that occurs at the divergent boundary in the far south of the state.

The rock is also quite pretty, to this geologist's eye. It ranges in color from black to intense jade-green. The journey from deep in the crust to the surface along fault zones usually leaves beautiful polished surfaces on the rock.

As to the state's choice for a symbolic gemstone, the state legislature made a great one: a stone that is not only found just in California, but is found at only one place in California, in a remote corner of San Benito County in the Coast Ranges. It is called Benitoite, and is a beautiful sapphire blue. The barium-titanium silicate mineral was declared our gemstone in 1985.

Benitoite has another distinction. There are 4,000 or so minerals known in the world, and they crystallize into 32 geometric classes. Out of all those minerals, benitoite is the only one that crystallizes ditrigonal-dipyramidial class in the hexagonal system.

The natural crystals occur in beautiful triangle patterns, seen in the picture below. Despite their rarity, one can visit the mine and screen the tailings for benitoite crystals, and other rare minerals, including neptunite. For a price, of course.

In the next post, the geologic story behind some of our animal symbols...

50 Minerals one must see....a geologic meme (and me too!)

Jumping on the bandwagon, here are the 50 minerals from Chuck's list that I have seen (See Lounge of the Lab Lemming and others here, here and here). Like Dave, I would have added more of my own, but I am at work after all. On the other hand, California is a dream site for finding strange and exotic minerals, and I am adding three to my list: Serpentine (yes, chrysotile, but I like the greasy form), because it is the California State Rock (legislature was supposed to call it serpentinite, but didn't know any better); gold, because it is our state mineral for obvious reasons, and seeing it in the wild is always a memorable experience; and benitoite, because it is our state gemstone, and it is found in gem quality specimens pretty much at a single mine in in San Benito County. It is also one of the first minerals discovered that crystallizes in the ditrigonal dipyramidal class, making for some beautiful triangular crystals. It is my picture of the day...

As Chuck says:

Use bold to indicate minerals you’ve seen in the wild. Italics is for those seen in laboratories, museums, stores, or other non field locations. Ex pet nerds may use underlining to indicate those that they’ve grown with their own two hands. And I won’t bother with stuff you intend on seeing- if you didn’t want to see all these minerals yourself, you’d be spending your precious lunch hour on a physics or biomedical blog.

Andalucite

Apatite

Barite

Beryl

Biotite

Chromite

Chrysotile

Cordierite

Corundum

Diamond

Dolomite

Florencite

Galena

Garnet

Graphite

Gypsum

Halite

Hematite

Hornblende

Illite

Illmenite

Kaolinite

Kyanite

Lepidolite

Limonite

Magnetite

Molybdenite

Monazite

Nepheline

Olivine

Omphacite

Opal

Perovskite

Plagioclase

Pyrite

Quartz

Rutile

Sanidine

Sillimanite

Silver (native)

Sphalerite

Staurolite

Sulphur (native)

Talc

Tourmaline

Tremolite

Turquoise

Vermiculite

Willemite

Zeolite

Zircon