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San Benito County
  
  Index -> Minerals and Mineralogy
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Roger Warin




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PostPosted: Mar 15, 2018 05:30    Post subject: San Benito County  

Hi,
It's always nice to admire a classic mineral combination: neptunite, benitoite and joaquinite-(Ce) ( San Benito County).

Neptunite and others are imbedded in thick natrolite, a zeolite.
Such a specimen is prepared by dissolving natrolite in diluted hydrochloric acid.



034-Benitoite_2_R.jpg
 Mineral: Neptunite, Benitoite, Joaquinite-(Ce)
 Locality:
San Benito County, California, USA
 Description:
 Viewed:  2304 Time(s)

034-Benitoite_2_R.jpg



035-Neptunite#2_R.jpg
 Mineral: Neptunite
 Locality:
San Benito County, California, USA
 Description:
 Viewed:  2298 Time(s)

035-Neptunite#2_R.jpg



036-Benitoite#1_R.jpg
 Mineral: Benitoite
 Locality:
San Benito County, California, USA
 Description:
 Viewed:  2297 Time(s)

036-Benitoite#1_R.jpg



037-Joaquinite#1-E_R.jpg
 Mineral: Joaquinite-(Ce)
 Locality:
San Benito County, California, USA
 Description:
 Viewed:  2306 Time(s)

037-Joaquinite#1-E_R.jpg


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Peter Lemkin




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PostPosted: Mar 15, 2018 05:38    Post subject: Re: San Benito County  

Yes, such nice specimens from this location. To bad it is said to now be extinct. I'm not sure that there are no more XX available, but apparently the mining operation is over and has been filled in. A unique location for sure.
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Jesse Fisher




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PostPosted: Mar 15, 2018 10:59    Post subject: Re: San Benito County  

It is my understanding that the locality is essentially finished. However, there are at least two folks I am aware of who acquired fair amounts of unprocessed material from the mine prior to closure, and are continuing to process it and bring specimens to the market.
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Pete Modreski
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PostPosted: Mar 15, 2018 13:26    Post subject: Re: San Benito County  

Really nice specimen and photos, Roger, thanks!
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GneissWare




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PostPosted: Mar 15, 2018 19:27    Post subject: Re: San Benito County  

Here are 2 I prepped awhile back.


RG1543.JPG
 Mineral: Benitoite, Neptunite, Joaquinite
 Locality:
California State Gem Mine (Benitoite Gem Mine), Dallas Gem Mine area, San Benito River headwaters area, New Idria District, Diablo Range, San Benito County, California, USA
 Dimensions: 69 x 58 x 27 mm
 Description:
Lustrous black prismatic crystals of Neptunite to 19 mm long with corn-flower-blue Benitoites to 13 mm partly cover a natrolite-coated plate of matrix. A single orange-brown crystal of Joaquinite to 1 mm is perched on one edge.
 Viewed:  2100 Time(s)

RG1543.JPG



RG1546.JPG
 Mineral: Benitoite, Neptunite
 Locality:
California State Gem Mine (Benitoite Gem Mine), Dallas Gem Mine area, San Benito River headwaters area, New Idria District, Diablo Range, San Benito County, California, USA
 Dimensions: 77 x 46 x 26 mm
 Description:
A pair of lustrous, black prismatic crystals of Neptunite to 21 x 6 mm balance a cornflower-blue Benitoite to 25 x 13 mm exposed from a natrolite-coated plate of matrix. Several smaller crystals of Benitoite and Neptunite are present.
 Viewed:  2098 Time(s)

RG1546.JPG


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JohnVeevaert




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PostPosted: Mar 17, 2018 14:22    Post subject: Re: San Benito County  

Here is some "rock solid" info re: the Benitoite Gem Mine. Bryan Lees finished with his project and rehab work in 2004. The property was sold to Dave Schreiner of Coalinga. Bryan exposed the entire original vein system - or at least where it was. It was entirely gone. He also worked the dump material and colluvial material through his jig system TWICE! The mud on the rocks there is tenacious meaning 5-10% of material that could produce a rock worth etching went through it and back into the new dumps. This material was used to fill in the large hole created and recontour the site for revegetation. Schreiner periodically goes up and hauls a 10 yard truck down the hill to Los Gatos park where folks can pay $70-$100 to screen material. It is kind of a rip because if you find anything that will etch out a good rock you have to negotiate a price to pay for it if you want to keep it and trust me no one knows what the hell is in these things until you start to etch them. In 2010 Steve Perry and I purchased all of Bryan's unprocessed mine material which was about 10 tons worth. We're down to the last 2.5 tons and fortunately it is decent stuff so we expect more good specimens for the next 5-7 years. If the area is ever reopened by BLM and EPA there will be a chance to find material at the mine site after a large rain. Good rocks covered in mud are still out there. But the mine will never again be able to produce on a commercial scale. There is more information at benitoite dot com.
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Peter Lemkin




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PostPosted: Mar 18, 2018 01:45    Post subject: Re: San Benito County  

Thanks for that authoritative reply. I used to live not that far away in San Diego, but never even tried to get permission just to see the site. Do you or anyone have any good references on articles about the mineralogy and geology of the claim area. I seem to remember one long ago in the Min. Record. [my copies of which I don't have with me here in Europe, sadly]. There are not many sites in the World where such beautiful minerals occur almost [or completely] uniquely. I imagine geologists have looked nearby to see if there might not be some other veins with more. Alas, none were found.
Although discovered earlier, I remember well when the specimens first started to show up regularly at Tuscon and other shows, never cheap...and now there are the last pieces being sold. I also love the Neptunite from this locality.

Type Locality:
ⓘ California State Gem Mine (Dallas Gem Mine; Benitoite Mine; Benitoite Gem Mine; Gem Mine), Santa Rita Peak, New Idria District, Diablo Range, San Benito Co., California, USA
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Jordi Fabre
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PostPosted: Mar 18, 2018 07:11    Post subject: Re: San Benito County  

Peter Lemkin wrote:
...Do you or anyone have any good references on articles about the mineralogy and geology of the claim area...

Some images about the locality:





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John S. White
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PostPosted: Mar 18, 2018 10:55    Post subject: Re: San Benito County  

Hey John: Ten tons is a heckuva lot of rock. I’ll bet that many FMFers, myself included, would be interested in learning of how all that rock was transported to you. We are used to thinking in terms of a backpack full of rocks.
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JohnVeevaert




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PostPosted: Mar 18, 2018 11:59    Post subject: Re: San Benito County  

You can go to benitoite dot com and there you'll find a large article I wrote on the deposit detailing the mineralogy and geology of the deposit and crystallography of benitoite. Here's the link to the article:
http://benitoite.com/benitoite/benitoite.pdf
(link normalized by FMF)
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