What's My Rock? #4 - a rock identification show

[@genefulm]

There was Kaiser Steel Mill in Fontana, CA (near San Bernardino) from 1941 to 1981. Massive production during WWII and the Korean war. It is likely they dumped the slag all over the place. Especially for road building.

[@sirism98]

Found bunch of these in Mill valley CA, about 10 years ago. I did landscaping and had to made stairs down the hills.

[@willyeverdie2731]

I think his process of elimination is spot on. It's easier to eliminate what it is not sometimes than say what it is. Look at his specimen storage in the foreground, he has been doing this for a minute let alone he has a degree and is using all the state of the art tools you can without being in a college mineralogy lab. This man has identified minerals for far more hours than your average rock enthusiast.

[@MostlyIC]

"ferro-silicon" is a thing, it is man-made, and used in the steel making process, silicon as you say prefers oxygen so adding it to molten iron helps to remove oxygen, as the silicon-dioxide floats to the surface, and to make "steel" there's always a little bit of pure silicon and pure manganese that has to be added to make the alloy, and those are not found in iron ore.

[@tectonic_city]

thank you! it all makes sense now as a metallurgical additive, silicon oxidation produces hydrogen (consumes oxygen) that helps to reduce the iron ore.

[@MostlyIC]

@@tectonic_city yes, its a tiny bit more complicated than that as its actually a two stage process, first iron ore is "smelted" where most of the oxygen is burned out by using carbon and turned into "pig iron", then the pig iron is remelted in a different kind of furnace and goes through a second step of refining where ferro-silicon and ferro-manganese are added as de-oxidizers and oxygen or air is bubbled through it to eliminate excess carbon, finally ending up with the alloy we call "steel".

[@tectonic_city]

thanks for the info. I wonder is this two-step process has to do with the fact that carbon is cheaper than native silicon, and in geochemical parlance the redox state of charcoal+iron is not as reducing as silicon+iron, so the pig iron is the cost-effective first-pass at reduction, and the silicon finishes it off. you could, after all, do it all in one step with silicon but that would not be cost effective. for that matter you could use titanium metal as an oxygen getter but that would probably be even more expensive.

[@MostlyIC]

@@tectonic_city it all depends on where the metal is on the reactivity scale, metals like aluminum, titanium, silicon, etc can't be smelted, carbon (coke, charcoal, etc) in the smelting process can't extract the oxygen from those oxides. carbon is very cheap, but aluminum, titanium, silicon, and manganese for example are expensive in comparison, mostly because they themselves cannot be purified by smelting, IE they are more reactive than carbon so carbon can't steal the oxygen from their oxide ores. so the silicon and manganese are added only in the second step where only very small amounts are needed, partly as de-oxidizers and party as desired alloy ingredients.

[@francesray6465]

Those two objects were found within 35 miles of Fontana. Fontana Steel was the west coasts largest steel producer up until the 1970s. The slags were used as railroad ballast, road base, landing strip base etc. all through the region.

[@AdrielG.]

Dr. Abstract, first of all I want to say thank you for this podcast. I have some information that I know will help you out in your - to do with all that smelting you've been running across. I can explain it I know you're busy guy, but if you could spare five minutes of your time I would be happy to I know you shouldn't give out your phone, that I'm doing it this is not a joke it will blow your mind. I hope to hear from you soon. Thanks again.

[@tectonic_city]

you're welcome, thanks for the offer, but it would be better for you to just post it right here as a comment for all to learn from

[@canadiangemstones7636]

Let me guess... ancient aliens?.. 😂

[@sarahb.6475]

People sure bring you the most unusual rocks!! I never would have thought silicon is a "rock"... That is a manmade rock.

[@tectonic_city]

I’m always learning something new with the things people bring me

[@Bizarreparade]

I found some ferrochrome in my yard. Thought it was a platinum nugget for a second until I realized how dumb that is. They used it in the steel making process which would make sense in SW PA😂

[@MostlyIC]

Dr Abstract, here's my rock: in the Sierra Nevada there's Garnet Lake, and its though to be named after the green, sometimes even sparkly when fresh, surfaces found on some granite, usually a very thin coating like there was a very thin crack in the rock that filled with this green stuff and then later split along it when the rock broke up exposing the green. but in my many wanderings in the Sierra I've found larger all green rocks, and even some all green boulders, that seem to be the exact same "green", so I'm almost certain this is not the actual garnet mineral, rather I suspect a serpentine or olivine. I've never seen a sample of this green rock in any Forest Service geology exhibit, but I find it fascinating, and am still hoping for an identification some day, what do you think ?

[@tectonic_city]

probably epidote veins (epidote is a pistachio green mineral common as a hydrothermal alteration product of granitic rocks)

[@AdrielG.]

Dr. Abstract have some information you can use regarding the smelting you've been running across. Is there anyway that we can speak over the phone. Or do you have an email address . I don't have an Instagram account. I feel I'm 100% on this and I would appreciate your professional opinion . Thanks again.

[@bookieone9277]

Ive been calling it a fusion crust all this time.

[@tectonic_city]

fusion crust is the correct technical term

[@DR_SOLO]

😂😂 i don't believe that but i believe everything else, you should believe it also.!!😅😅😊

[@geoffgeoff143]

The larger one looks like silicon.

[@tectonic_city]

Yup was our conclusion as well

[@williamcampbell5349]

Is it me or does this guy seem unsure of his own answers to his own statements...... The show idea is fabulous. ..A+ But they need a better geologist.

[@tectonic_city]

I'm happy to accept criticism, but it would be more helpful to provide a specific timestamp where you feel I'm being "unsure"

[@TinaHyde]

I wholeheartedly disagree. I think he did a great job explaining what their ‘rocks’ could possibly be and an even better job explaining why they definitely were not meteorites. Just the fact alone that he does not proclaim with 100% certainty what they are tells me he’s a good geologist. 👌

[@Unk13Dave]

He is just being diplomatic so he doesn't hurt people's feelers

[@Bizarreparade]

Theres always one😂😂😂