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Let's Rock => Identifications of Materials => Deceptive Stones => Topic started by: crustygem on January 25, 2018, 04:26:08 PM

Title: Not obsidian!?!
Post by: crustygem on January 25, 2018, 04:26:08 PM: Ok so here is a beautiful black....something! It was the only one like this on the beach or at tide line. When I first saw it I thought obsidian, as it was wet and shiny, score! Would have been my first. However, when I got home and it had dried off it's obviously NOT obsidian. I thought maybe jet? I did gravity test, and again my scale is older and maybe not so accurate, and got 1.97
Steel will not scratch, diamond will.
It has a greenish streak I tried to get a good pic of. I love it!!(https://uploads.tapatalk-cdn.com/20180126/9c4c84835a083da1f22dea17c1dffbcd.jpg)(https://uploads.tapatalk-cdn.com/20180126/641d453580f9dcdf69960ed739e10490.jpg)(https://uploads.tapatalk-cdn.com/20180126/4070563c1cdb7af0e4b028119a3c6f2b.jpg)(https://uploads.tapatalk-cdn.com/20180126/e79261efada2813f9c35e7c51a6e7ce8.jpg)(https://uploads.tapatalk-cdn.com/20180126/6e2791e5bc3c7d1bea5c13e80e4b6308.jpg)(https://uploads.tapatalk-cdn.com/20180126/52767066e552fd347076f403d4931982.jpg)

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Title: Re: Not obsidian!?!
Post by: 55fossil on January 25, 2018, 04:47:31 PM: Is it green under all that black skin????? Trying to see if it is mafic or a basalt type material?
Title: Re: Not obsidian!?!
Post by: crustygem on January 25, 2018, 04:49:05 PM: Quote from: 55fossil on January 25, 2018, 04:47:31 PM
Is it green under all that black skin????? Trying to see if it is mafic or a basalt type material?
Well, when I scrape it it is still black

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Title: Re: Not obsidian!?!
Post by: crustygem on January 25, 2018, 04:52:35 PM: Quote from: crustygem on January 25, 2018, 04:49:05 PM
Quote from: 55fossil on January 25, 2018, 04:47:31 PM
Is it green under all that black skin????? Trying to see if it is mafic or a basalt type material?
Well, when I scrape it it is still black

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Check out fracture lines(https://uploads.tapatalk-cdn.com/20180126/a5831fa806fde1cdc2d90d2d2e1556d9.jpg)

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Title: Re: Not obsidian!?!
Post by: lapidaryrough on January 25, 2018, 05:59:08 PM: Hematite is 97.5% Si;ica & 2.5% Iron. Alaska's Sate rock.
Botrydole formations. nice material.
Title: Re: Not obsidian!?!
Post by: crustygem on January 25, 2018, 07:32:29 PM: Quote from: lapidaryrough on January 25, 2018, 05:59:08 PM
Hematite is 97.5% Si;ica & 2.5% Iron. Alaska's Sate rock.
Botrydole formations. nice material.
I don't think it's hematite. It's specific gravity is way too low. Also I think it's hardness is more than hematite(https://uploads.tapatalk-cdn.com/20180126/4d5e5150694d5136158bc063d96ad5cc.jpg)

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Title: Re: Not obsidian!?!
Post by: crustygem on January 25, 2018, 07:32:53 PM: Quote from: crustygem on January 25, 2018, 07:32:29 PM
Quote from: lapidaryrough on January 25, 2018, 05:59:08 PM
Hematite is 97.5% Si;ica & 2.5% Iron. Alaska's Sate rock.
Botrydole formations. nice material.
I don't think it's hematite. It's specific gravity is way too low. Also I think it's hardness is more than hematite(https://uploads.tapatalk-cdn.com/20180126/4d5e5150694d5136158bc063d96ad5cc.jpg)

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This is the pic I have for hematite

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Title: Re: Not obsidian!?!
Post by: crustygem on January 25, 2018, 07:33:34 PM: Quote from: crustygem on January 25, 2018, 07:32:53 PM
Quote from: crustygem on January 25, 2018, 07:32:29 PM
Quote from: lapidaryrough on January 25, 2018, 05:59:08 PM
Hematite is 97.5% Si;ica & 2.5% Iron. Alaska's Sate rock.
Botrydole formations. nice material.
I don't think it's hematite. It's specific gravity is way too low. Also I think it's hardness is more than hematite(https://uploads.tapatalk-cdn.com/20180126/4d5e5150694d5136158bc063d96ad5cc.jpg)

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This is the pic I have for hematite

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Also it's not magnetic.

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Title: Re: Not obsidian!?!
Post by: Phishisgroovin on January 25, 2018, 08:15:15 PM: magnatite i bet
Title: Re: Not obsidian!?!
Post by: Slabbercabber on January 26, 2018, 05:06:51 AM: That seems pretty light but I would still bet on high alumina basalt.
Title: Re: Not obsidian!?!
Post by: christos on November 14, 2023, 07:08:51 PM: looks like iron ore silicate prob as stayed with alum silate.. i find similiar in red and green tones at an ancient quarry near a riverwhere an ancient volcano flowed. unless the similiarity
Title: Re: Not obsidian!?!
Post by: lithicbeads on November 15, 2023, 04:41:44 PM: Any classically trained geologist upon encountering a thoroughly black stone on the beach would say hornfels. Rockhounds never say hornfels.
Title: Re: Not obsidian!?!
Post by: christos on November 18, 2023, 12:37:28 PM: Quote from: crustygem on January 25, 2018, 04:26:08 PM
Ok so here is a beautiful black....something! It was the only one like this on the beach or at tide line. When I first saw it I thought obsidian, as it was wet and shiny, score! Would have been my first. However, when I got home and it had dried off it's obviously NOT obsidian. I thought maybe jet? I did gravity test, and again my scale is older and maybe not so accurate, and got 1.97
Steel will not scratch, diamond will.
It has a greenish streak I tried to get a good pic of. I love it!!(https://uploads.tapatalk-cdn.com/20180126/9c4c84835a083da1f22dea17c1dffbcd.jpg)(https://uploads.tapatalk-cdn.com/20180126/641d453580f9dcdf69960ed739e10490.jpg)(https://uploads.tapatalk-cdn.com/20180126/4070563c1cdb7af0e4b028119a3c6f2b.jpg)(https://uploads.tapatalk-cdn.com/20180126/e79261efada2813f9c35e7c51a6e7ce8.jpg)(https://uploads.tapatalk-cdn.com/20180126/6e2791e5bc3c7d1bea5c13e80e4b6308.jpg)(https://uploads.tapatalk-cdn.com/20180126/52767066e552fd347076f403d4931982.jpg)

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did you tryanother SG test with a smaller piece?