Nick_Huntington
Joined: 17 Sep 2019
Posts: 1
Location: California
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Posted: Apr 10, 2020 20:11 Post subject: Any help would be appreciated |
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Hello, I found these last year while doing some work in a vineyard near Lake Sonoma. The reddish areas have a waxy luster and a streak that is reddish brown (was hard to get it to leave a streak).
I chipped off a piece from a larger rock I couldn't get loose and had to leave there. The chipped off piece has a lot of different things going on with it. That photo is of the freshly exposed side. The other side of it is similar to the look of the other samples.
The different pieces I found have slightly different heft to them and I have gotten specific gravity calculations from 3.4 to 4.1.
There are some old manganese prospects in the area and several outcroppings of chert with black manganese oxides on the property so I was guessing this is one of the manganese silicates for the areas with red/pink/yellow color but unsure of what the small grey/black crystals are. Any thoughts about what minerals are making up these rocks would be welcome.
Thanks,
Nick Huntington
Mineral: | Manganese silicates? and ? |
Locality: | Sonoma Lake area, Sonoma County, California, USA | ![](templates/FabreMinerals/images/LocalidadesGreen.png) |
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Dimensions: | 2cm by 3cm |
Description: |
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11861 Time(s) |
![Sample 1.jpg](files/thumbs/t_sample_1_673.jpg)
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Mineral: | Manganese silicates? and ? |
Locality: | Sonoma Lake area, Sonoma County, California, USA | ![](templates/FabreMinerals/images/LocalidadesGreen.png) |
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Dimensions: | 4cm |
Description: |
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11858 Time(s) |
![Sample 2.jpg](files/thumbs/t_sample_2_139.jpg)
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Mineral: | Manganese silicates? and ? |
Locality: | Sonoma Lake area, Sonoma County, California, USA | ![](templates/FabreMinerals/images/LocalidadesGreen.png) |
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Dimensions: | Ruler is in inches |
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11869 Time(s) |
![Samples with ruler.jpg](files/thumbs/t_samples_with_ruler_201.jpg)
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Description: |
Streak of the reddish waxy area |
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11867 Time(s) |
![Streak.jpg](files/streak_138.jpg)
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Mineral: | Manganese silicates? and ? |
Locality: | Sonoma Lake area, Sonoma County, California, USA | ![](templates/FabreMinerals/images/LocalidadesGreen.png) |
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Dimensions: | 25cm x 8cm |
Description: |
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11869 Time(s) |
![Chipped off sample.jpg](files/thumbs/t_chipped_off_sample_697.jpg)
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Mineral: | Manganese silicates? and ? |
Locality: | Sonoma Lake area, Sonoma County, California, USA | ![](templates/FabreMinerals/images/LocalidadesGreen.png) |
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Dimensions: | 4cm by 3cm |
Description: |
Close up of area on left side of chipped off sample |
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11860 Time(s) |
![Closeup of chipped off sample.jpg](files/thumbs/t_closeup_of_chipped_off_sample_762.jpg)
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Mineral: | Manganese silicates? and ? |
Locality: | Sonoma Lake area, Sonoma County, California, USA | ![](templates/FabreMinerals/images/LocalidadesGreen.png) |
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Dimensions: | 24cm by 12cm |
Description: |
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11865 Time(s) |
![Large sample.jpg](files/thumbs/t_large_sample_157.jpg)
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Mineral: | Manganese silicates and ? |
Locality: | Sonoma Lake area, Sonoma County, California, USA | ![](templates/FabreMinerals/images/LocalidadesGreen.png) |
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Dimensions: | about 4cm by 3cm |
Description: |
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11859 Time(s) |
![Large sample closeup.jpg](files/thumbs/t_large_sample_closeup_566.jpg)
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Mineral: | Manganese silicates? and ? |
Locality: | Sonoma Lake area, Sonoma County, California, USA | ![](templates/FabreMinerals/images/LocalidadesGreen.png) |
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Dimensions: | about 3cm x 2cm |
Description: |
close up photo of the chipped off piece |
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11863 Time(s) |
![Close up 1.jpg](files/thumbs/t_close_up_1_212.jpg)
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Jordi Fabre
Overall coordinator of the Forum
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Joined: 07 Aug 2006
Posts: 4906
Location: Barcelona
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Posted: Apr 29, 2020 14:03 Post subject: Re: Any help would be appreciated |
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Massive minerals and rocks are not easy to determine Nick. We can say a lot of guesses but just by a photo and without distinctive details I'm afraid that you need go to some Show or mineral club close your area and ask there if some one is familiar with what you have.
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Bob Harman
Joined: 06 Nov 2015
Posts: 765
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Posted: Apr 29, 2020 14:36 Post subject: Re: Any help would be appreciated |
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Agree with Jordi. Also, being rocks and not a mineral, specific gravity and streak have little meaning as they are meant primarily for minerals.
Bob
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Bob Carnein
Joined: 22 Aug 2013
Posts: 331
Location: Florissant, CO
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Posted: Apr 29, 2020 18:16 Post subject: Re: Any help would be appreciated |
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You need to try the streak of the black mineral. My guess is that it will turn out to be hematite, which has a red-brown streak.
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