Please LIKE and SUBSCRIBE. I also appreciate your continual support of these geology education videos. To do so, click on the "Thanks" button just above (right of Download button) or by going here: www.paypal.com/donate/?hosted_button_id=EWUSLG3GBS5W8 Or: www.buymeacoffee.com/shawnwillsey
Thanks Shawn. Decompression melting is certainly an important concept to understand. The analogy of water's boiling point at different altitudes/atmospheric pressure helps my brain for some reason.
Very interesting! That explains the content of the Black Hills granites and pegmatites of quartz, white feldspar, muscovite mica, and black tourmaline! It's felsic granite.
I remember asking you a few months ago on a Q&A what was the difference between magma and lava. This seems to be some of the much more detailed explanation of your answer from back then. Thank you Shawn!
Where were you when I was doing my degree!? (Pointless question, it was many decades ago now). But, oh, how I wish this had been available then! I was never very good with the chemistry part of geology (having a physics background) but your little diagram just clicked a lightbulb on in my head and bits of knowledge are starting to make more sense. I fear I will be disappearing down a rabbit-hole of research shortly, I still have my old books. Thank you for this series. I won’t ever do anything practical with it at my age and decrepitude but all knowledge is worth having.
Thank you so much for all the great content. I am an automotive technician during the day but always have a curious mind. Your videos along with other great channels help put together a more complete understanding of the world around me and in some cases help in my own profession…. All pieces to a grand puzzle my friend!
How can I possibly watching your lessons for a year and STILL LEARNING or grasping concepts as if never heard before. Love the Ah-Hah lightbulb click on in my head. THANK YOU
Thank you, Shawn! Just started to have a listen while working around the house before bed! Sorry I’ve been extremely busy which is why I haven’t like or commented recently! It is a honor, and privilege to learn the science of geology! So well conveyed! I also, hope all is well! 🪨🏔️🌋
My unsolicited advice. The greatest thing you can learn from Geology is a sense of the long now and deep time. So give all of these lessons, the time to complete them and find homework assignments you can work yourself so you really understand the dynamics of what is discussed. Start at the beginning. Work your way to the end. Good luck.
Does Felsic, Intermediate or Mafic types of maga influence whether lava flow is more likely to be Pāhoehoe vs 'A'ā ? Or is terrain more determinative (fast moving vs slow moving because of no incline) in whether the lava will be one or the other?
Fluid mechanics of water and steam is right up my street, but adding rock chemistry into the equation is a totally new subject for me! Looking forward to the follow up sessions. 👌
If you have time, please cover feldspathoids, like nepheline and sodalite. I assume they crystalize at lower temperatures where there's not enough Si and O to form quartz.
How about #4. A volcano erupts and builds a mountain like Rainier which puts more pressure on the magma below, it melts and the center of the volcano drops...like mt. st. helens. Mt. Narahoe (spelling) in N. island of New Zealand seems to produce a lot of scoria, pumice. The center lake is full of acid that flows out a river into a river that will bleach the skin on your hands.
Thanks Shawn, this is an eye opener for me. I thougt lava was either basalt or has more silica (creating obsidian in some cases) Now gasses get into the mix, faultlines etc. and things become really complicated...
Gah! This topic keeps drawing me in! 😱🤗 This is fascinating stuff! I see how you read landscapes as quickly as you do with your Random Roadcut Videos. I found myself doing something I last did in primary school when I took walks: I started picking up interesting looking rocks on my walks. 🤭😇 As I live near Bonn where the landscape´s surface had mainly been formed in the late ice age, the stones here are a complete hodge podge dropped by the moraines, so there's no context to them. Still… 🤩
Thank you for another great lesson, Shawn, it keeps my more mature brain active. I think I would have found it harder to follow, having an arts based degree rather than science based, if I hadn't watched your 'Minerals with Willsey' series. I will need to rewatch this and dive into your series on rocks as well.
29:17 the correct answer is D Amphibole and here is why Quartz, Quartzsite, Mica, and Calcite which are crystals require low viscosity magma or they will melt because they are made of silica. We know its not Olivine or Sulfur because those require high viscosity magma and those are the first to come out in a violent eruption with the rhyolite bombs. That leaves Amphibole as the answer Aqua also forms at that temperature both require medium heat in order to form.
Excellent content, many thanks as always Shawn! The problem is, the more I learn and try to remember, the more I realize there is so much more to learn and to remember... and I'm not getting any younger, which doesn't help! ;)
so a quartz vein would be formed from high pressure, relatively low temperature....letting it flow into tiny cracks. then when cooling other things drop out like gold, galena, and pyrites.
Love this! PhD geology and I thought the subducted plate melted 😂 . So does the water lower the melting temperature of the obducting plate? How would this look on a pressure temperature plot 🤔
I was reading a news story about moon geology and I turned to you to help me understand a paper on a moon rock. Apparently the moon is a giant volcano geologically.
I just drove by some bada@$ basaltic sills (andesitic?) at Malibu/Hueneme on Hwy 1, arguably one of the top three coastal road stretches on the west coast. I understand this is the primary fissure zone for the Channel Islands volcanics. Age is easily available on google I would suspect.
In this video towards end, you mention Felsic tends to be more bouyant and Mafic dropping to bottom of reservoir. During the 2018 Kilaeua eruption, there was mention of East rift zone initially spewing out older lava and later spewing out younger lava piping hot and fresh from the reservoir under kilauea. Was this differentiation old vs new due to felsic, Intermediate, Mafic composition, or just due to temperatoure or disolved gas content?
I would note that on rare circumstances the downwelling slab itself can melt into what are termed adakite series melts, it is just this doesn't happen much on modern Earth but very rarely typically if either young ocean lithosphere and or a mantle plume is present you can still get these kinds of rocks. This appears to have happened between 20 and 30 million years ago in the Cascadia Subduction zone Pacific Northwest. As for incompatible minerals convective mixing can kind of screw with that the chemistry in mixing magmas get insane and extremely dynamic. So Peridotite is the intrusive counterpart of Komatiite now we are not likely to see that magma type anymore barring extreme circumstances as Earth's mantle has cooled off but it is one of the most fascinating and terrifying super low viscosity. So next time is the specifics of igneous rock types I'm guessing you will talk about Alkalinity there? After all alkaline magmas are another dimension which gives you some other weird chemistry and magma types they get very confusing what with stuff like basanite shoshonite phonolite trachyte and the various word salads like Mt Etna's basaltic trachyandesite or Campi Flegrei's trachyphonolite. I noticed some combinations are more common for instance trachyte and basalt are much more common as a prefix. But even Rhyolite occasionally is used this may i.e. rhyodacite. It is so confusing especially with alkalinity not seeming to be accounted for with rhyolites. Oh and there are also pegmatites another weird igneous series of very water dominated melts known for their ability to rapidly form large spectacular crystals. And then of course you also have the crazy weird Carbonatite magmas of which only Ol Doinyo Lengai is currently erupting.
Question: if magma that is the right tempetature to be rich in Olivine comes out as a nice fountain in my backyard, what happens to the olivine as the lava cools down? In your video you mention it may decompose into other minerals if the magma cools down. Does rate of lava cooling affect whether it decomposes or remain as olivine? Or will some olivine always remain irrespective of cooling while other will decompose into other minerals as it cools?
Is it partial melting and recrystallization that explains why arctic explorers found that the salinity of old (multiyear) arctic sea ice had been reduced to the point that it (multiyear ice) could be melted for drinking water?
So I have a question ! What motivates plate tectonics as in Iceland where there are divergent plates, is it the magma coming up and forcing the plates to move ?
Iceland exists because there is also a hot spot located there. Some geologists suspect that the subducting plates apply a dragging force on the divergent plate boundaries which allows the upwelling magma to reach the surface and spread out, while others suspect the upwelling is pushing the plates apart. There is evidence supporting both scenarios. It is likely a combination of factors.
If you melted Ryolite (maybe hot as possible?) could you then cool it quickly in water or ice to make obsidian? If so; then what elements would you add to get colors like in rainbow obsidian or fire obsidian or snowflake obsidian?
Is it too simplistic to say, because quartz melts at a lower temperature, that is the reason we have several quartzite topped mountain's i.e. quartz melt is at the top of the melt ?
I have hydrothermal vent with dolomite Magnitite Limonite after pyrite native copper iron gold chromium magnesium basalt limestone pegmitite platinum copper after cuprite mica schist Garnets Serpentine slate siver sapphires turmoline obsidian kimberlite host rocks emerald ruby valintinite jade sapphire glass naturally transparent and no one will help me because I am a amiture and a girl. It is a Hotspot from the cambrian era! You helped me understand at this point I am ready to do a sit it at the Smithsonian till someone listens. My situation is exactly what you describe at 9:08 we were brackish peat bog om the edge of the great magnesium patch we were a weak point from there crush and separation dolomite but we were last under water at cambrian it's a kimberlite tube formation but has a path like a Hotspot. Pease I need help. No one in my state is talking to me. I thought about a journal but I'm so confused about how to format it. I did get an orchis number.
When Olivine needs temperatures above ca. 1000°C, how come we ever see it on the surface of Earth? Assumption A: The crystals get trapped by other crystals that form at lower temperature; assumption B: Olivine crystals "freeze" when the melt cools down further; assumption C: My misunderstanding of Bowen's reaction series - it shows the conditions under which crystals form, but not necessarily those when they decay; assumption D: none of the above, or a combination. @shawnwillsey can you please help?
On second thought, I assume the reaction series shows the conditions under which crystals form, they melt when it gets hotter, but they don't decay when it gets colder. Is that right?
Erosion can expose outcrops that contain Olivine. I have found Olivine in volcanic rocks at the Kilbourne Hole in New Mexico, at the Calaveras Volcano in Carlsbad, CA, and in igneous rocks at a gold claim outside of Yuma, AZ. I also found a rare piece of Peridotite (a type of Olivine) at the Yuma location. The gold claim is on a volcanic field. There is a greenish beach in Hawaii that contains many, many tiny crystal of Olivine that have eroded out of a lava flow that made it to the ocean. Volcanic eruptions and erosion are two factors.
@@hansschleichert7852 Olivine does decay with time due to erosion but Olivine is fairly hard, with a mhos hardness of 6.5-7. In it's purest form, it is also called Peridot and can be faceted and used in jewelry.
Why doesn't the Mg, Fe,Si, and O continue to form olivine until one element is used up leaving nothing behind to create amphibole as the magma continues to cool?
Just tried to add water to a rock I found and it didn't melt 😞Am curious on the physics/chemistry that would cause water to melt rocks, I assume this is with rocks that are already very hot and prevented from melting by pressure?
The water is added to the chemical structure of the sedimentary rocks in the deep ocean under high pressure as they are formed. The rock doesn't appear wet or anything like that, but you would notice a loss of mass and a change in its chemistry as you heated the water out of it. In a subduction zone, that liberated water changes the chemistry of the rocks above it, making them melt more easily.
@@TheStormpilgrim Thanks for explanation. Does this mean that water in rocks ins't truly water but rather decomposed H2 and O that chemically combine with the minerals thereby changing melting point?
Please LIKE and SUBSCRIBE. I also appreciate your continual support of these geology education videos. To do so, click on the "Thanks" button just above (right of Download button) or by going here: www.paypal.com/donate/?hosted_button_id=EWUSLG3GBS5W8 Or: www.buymeacoffee.com/shawnwillsey
Mafic and Felsic are actually acronyms. Mafic = Ma(gnesium) + F(errum -iron) + silicate(silicon and oxygen) and Felsic = Fel(dspar) + Si(licate) (usually quartz).
I love that drawing, that's a really helpful visualization
I am so grateful that you are sharing these lessons with us for free. Thank you very much!
Thanks Shawn. Decompression melting is certainly an important concept to understand. The analogy of water's boiling point at different altitudes/atmospheric pressure helps my brain for some reason.
Nothing like geology for Sunday breakfast!
Shawn, thanks for creating these videos. I always regretted not taking a geology class in college, and so, I really appreciate this series.
Very interesting! That explains the content of the Black Hills granites and pegmatites of quartz, white feldspar, muscovite mica, and black tourmaline! It's felsic granite.
Fascinating about melt composition changing. Never understood before. Thanks for your drawing!
Thank you Shawn. This episode cleared up some of my confusion about igneous rocks and helped me get a better grasp of the Bowen Reaction Series.
Glad to help! Thank you.
I remember asking you a few months ago on a Q&A what was the difference between magma and lava. This seems to be some of the much more detailed explanation of your answer from back then. Thank you Shawn!
I am loving this series thank you so much. Everything is explained so plainly much appreciated
Thanks very much! I look forward to each episode in the series, and all your other presentations.
That gets more and more interesting! Thank you very much, Shawn.
Where were you 40 years ago? Understandable phase diagrams 101. Thanks for the series, always enjoy.
Where were you when I was doing my degree!? (Pointless question, it was many decades ago now). But, oh, how I wish this had been available then! I was never very good with the chemistry part of geology (having a physics background) but your little diagram just clicked a lightbulb on in my head and bits of knowledge are starting to make more sense. I fear I will be disappearing down a rabbit-hole of research shortly, I still have my old books. Thank you for this series. I won’t ever do anything practical with it at my age and decrepitude but all knowledge is worth having.
Great lesson. I was always science phobic in high school, but thankfully university life sparked an interest. Thanks again for all of these videos.
This was in my reccomsndations
That’s how I found him too 😊
Thank you so much for all the great content. I am an automotive technician during the day but always have a curious mind. Your videos along with other great channels help put together a more complete understanding of the world around me and in some cases help in my own profession…. All pieces to a grand puzzle my friend!
Great to hear!
How can I possibly watching your lessons for a year and STILL LEARNING or grasping concepts as if never heard before. Love the Ah-Hah lightbulb click on in my head. THANK YOU
Wow, thanks!
A little more understandable than just the chart of Bowen's Reaction Series. I took geology in Florida in the late 1960s. Thank you.
Thank you, Shawn! Just started to have a listen while working around the house before bed! Sorry I’ve been extremely busy which is why I haven’t like or commented recently!
It is a honor, and privilege to learn the science of geology! So well conveyed! I also, hope all is well! 🪨🏔️🌋
And a big thank you for very intelligent and well done presentations (which unfortunatly cause me to have questions because it makes me interested).
This was very instructive, and something I totally forgot from Geoology101 I took 36 years ago.
Been looking forward to this episode. Thank you!
Geology with Coffee! The best mix of all!
Just saw you and Nick Z. Keep it up. You guys rock the world with new ideas.
Thanks Shawn!! Love your content!
My unsolicited advice. The greatest thing you can learn from Geology is a sense of the long now and deep time. So give all of these lessons, the time to complete them and find homework assignments you can work yourself so you really understand the dynamics of what is discussed. Start at the beginning. Work your way to the end. Good luck.
Thank you 👍 Di..Cumbria.
Does Felsic, Intermediate or Mafic types of maga influence whether lava flow is more likely to be Pāhoehoe vs 'A'ā ? Or is terrain more determinative (fast moving vs slow moving because of no incline) in whether the lava will be one or the other?
Oh my gosh 😅! How did I miss this ? Will enjoy watching! Thanks Shawn Willsey 🙏🏼🌸🌼🌷☺️☺️
Fluid mechanics of water and steam is right up my street, but adding rock chemistry into the equation is a totally new subject for me! Looking forward to the follow up sessions. 👌
I liked the diagram and explaining the crystals forming. I think, I hope at least, that I will remember olivine forms first.
If you have time, please cover feldspathoids, like nepheline and sodalite. I assume they crystalize at lower temperatures where there's not enough Si and O to form quartz.
How about #4. A volcano erupts and builds a mountain like Rainier which puts more pressure on the magma below, it melts and the center of the volcano drops...like mt. st. helens.
Mt. Narahoe (spelling) in N. island of New Zealand seems to produce a lot of scoria, pumice. The center lake is full of acid that flows out a river into a river that will bleach the skin on your hands.
Very informative , thanks for the video .
Really enjoyed this lecture. I never knew there was a rock cycle!
Thanks Professor, very well done!
Thanks for all the hard work on these videos!
Great graphic on melt crystallization
This presentation has increased my appreciation of my quartz kitchen countertops! ❤️
Thank you!
Thanks!
Thanks Shawn, this is an eye opener for me. I thougt lava was either basalt or has more silica (creating obsidian in some cases) Now gasses get into the mix, faultlines etc. and things become really complicated...
Gah! This topic keeps drawing me in! 😱🤗 This is fascinating stuff! I see how you read landscapes as quickly as you do with your Random Roadcut Videos. I found myself doing something I last did in primary school when I took walks: I started picking up interesting looking rocks on my walks. 🤭😇 As I live near Bonn where the landscape´s surface had mainly been formed in the late ice age, the stones here are a complete hodge podge dropped by the moraines, so there's no context to them. Still…
🤩
Thank you for another great lesson, Shawn, it keeps my more mature brain active. I think I would have found it harder to follow, having an arts based degree rather than science based, if I hadn't watched your 'Minerals with Willsey' series. I will need to rewatch this and dive into your series on rocks as well.
Glad it was helpful!
29:17 the correct answer is D Amphibole and here is why Quartz, Quartzsite, Mica, and Calcite which are crystals require low viscosity magma or they will melt because they are made of silica. We know its not Olivine or Sulfur because those require high viscosity magma and those are the first to come out in a violent eruption with the rhyolite bombs. That leaves Amphibole as the answer Aqua also forms at that temperature both require medium heat in order to form.
Thanks Shawn great video again!
Oh dear. I think I need to go back and revise this episode! My brain is not what it used to be.......
Excellent content, many thanks as always Shawn! The problem is, the more I learn and try to remember, the more I realize there is so much more to learn and to remember... and I'm not getting any younger, which doesn't help! ;)
So pouring water on the Wicked Witch of the East really did melt her.
¡Gracias!
Many thanks for your support.
Hi, loving the course content so far! The playlist is in the wrong order though, would be great if that could be fixed :)
Thank you for this interesting series of videos. @25:00 there's a typo. The Celsius temperature of intermediate magma isn't 700 C.
It amazes me how even the tallest hard rock mountains can be worn down to nothing given time.
so a quartz vein would be formed from high pressure, relatively low temperature....letting it flow into tiny cracks. then when cooling other things drop out like gold, galena, and pyrites.
Thx Prof ✌🏻
Very clear. Question -- how does the molecular structure of the molecules relate to the structure of the crystals?
Love this! PhD geology and I thought the subducted plate melted 😂 . So does the water lower the melting temperature of the obducting plate? How would this look on a pressure temperature plot 🤔
I was reading a news story about moon geology and I turned to you to help me understand a paper on a moon rock. Apparently the moon is a giant volcano geologically.
I just drove by some bada@$ basaltic sills (andesitic?) at Malibu/Hueneme on Hwy 1, arguably one of the top three coastal road stretches on the west coast. I understand this is the primary fissure zone for the Channel Islands volcanics. Age is easily available on google I would suspect.
In this video towards end, you mention Felsic tends to be more bouyant and Mafic dropping to bottom of reservoir.
During the 2018 Kilaeua eruption, there was mention of East rift zone initially spewing out older lava and later spewing out younger lava piping hot and fresh from the reservoir under kilauea.
Was this differentiation old vs new due to felsic, Intermediate, Mafic composition, or just due to temperatoure or disolved gas content?
I would note that on rare circumstances the downwelling slab itself can melt into what are termed adakite series melts, it is just this doesn't happen much on modern Earth but very rarely typically if either young ocean lithosphere and or a mantle plume is present you can still get these kinds of rocks. This appears to have happened between 20 and 30 million years ago in the Cascadia Subduction zone Pacific Northwest.
As for incompatible minerals convective mixing can kind of screw with that the chemistry in mixing magmas get insane and extremely dynamic.
So Peridotite is the intrusive counterpart of Komatiite now we are not likely to see that magma type anymore barring extreme circumstances as Earth's mantle has cooled off but it is one of the most fascinating and terrifying super low viscosity.
So next time is the specifics of igneous rock types I'm guessing you will talk about Alkalinity there? After all alkaline magmas are another dimension which gives you some other weird chemistry and magma types they get very confusing what with stuff like basanite shoshonite phonolite trachyte and the various word salads like Mt Etna's basaltic trachyandesite or Campi Flegrei's trachyphonolite. I noticed some combinations are more common for instance trachyte and basalt are much more common as a prefix. But even Rhyolite occasionally is used this may i.e. rhyodacite. It is so confusing especially with alkalinity not seeming to be accounted for with rhyolites.
Oh and there are also pegmatites another weird igneous series of very water dominated melts known for their ability to rapidly form large spectacular crystals.
And then of course you also have the crazy weird Carbonatite magmas of which only Ol Doinyo Lengai is currently erupting.
Three types of rock: Ingenious, Sedentary, and Metaphoric.
Question: if magma that is the right tempetature to be rich in Olivine comes out as a nice fountain in my backyard, what happens to the olivine as the lava cools down? In your video you mention it may decompose into other minerals if the magma cools down. Does rate of lava cooling affect whether it decomposes or remain as olivine? Or will some olivine always remain irrespective of cooling while other will decompose into other minerals as it cools?
Is it partial melting and recrystallization that explains why arctic explorers found that the salinity of old (multiyear) arctic sea ice had been reduced to the point that it (multiyear ice) could be melted for drinking water?
So I have a question ! What motivates plate tectonics as in Iceland where there are divergent plates, is it the magma coming up and forcing the plates to move ?
Iceland exists because there is also a hot spot located there. Some geologists suspect that the subducting plates apply a dragging force on the divergent plate boundaries which allows the upwelling magma to reach the surface and spread out, while others suspect the upwelling is pushing the plates apart. There is evidence supporting both scenarios. It is likely a combination of factors.
If you melted Ryolite (maybe hot as possible?) could you then cool it quickly in water or ice to make obsidian? If so; then what elements would you add to get colors like in rainbow obsidian or
fire obsidian or snowflake obsidian?
Is it too simplistic to say, because quartz melts at a lower temperature, that is the reason we have several quartzite topped mountain's i.e. quartz melt is at the top of the melt ?
I have hydrothermal vent with dolomite Magnitite Limonite after pyrite native copper iron gold chromium magnesium basalt limestone pegmitite platinum copper after cuprite mica schist Garnets Serpentine slate siver sapphires turmoline obsidian kimberlite host rocks emerald ruby valintinite jade sapphire glass naturally transparent and no one will help me because I am a amiture and a girl. It is a Hotspot from the cambrian era! You helped me understand at this point I am ready to do a sit it at the Smithsonian till someone listens.
My situation is exactly what you describe at 9:08 we were brackish peat bog om the edge of the great magnesium patch we were a weak point from there crush and separation dolomite but we were last under water at cambrian it's a kimberlite tube formation but has a path like a Hotspot. Pease I need help. No one in my state is talking to me. I thought about a journal but I'm so confused about how to format it. I did get an orchis number.
When Olivine needs temperatures above ca. 1000°C, how come we ever see it on the surface of Earth? Assumption A: The crystals get trapped by other crystals that form at lower temperature; assumption B: Olivine crystals "freeze" when the melt cools down further; assumption C: My misunderstanding of Bowen's reaction series - it shows the conditions under which crystals form, but not necessarily those when they decay; assumption D: none of the above, or a combination. @shawnwillsey can you please help?
On second thought, I assume the reaction series shows the conditions under which crystals form, they melt when it gets hotter, but they don't decay when it gets colder. Is that right?
Erosion can expose outcrops that contain Olivine. I have found Olivine in volcanic rocks at the Kilbourne Hole in New Mexico, at the Calaveras Volcano in Carlsbad, CA, and in igneous rocks at a gold claim outside of Yuma, AZ. I also found a rare piece of Peridotite (a type of Olivine) at the Yuma location. The gold claim is on a volcanic field. There is a greenish beach in Hawaii that contains many, many tiny crystal of Olivine that have eroded out of a lava flow that made it to the ocean. Volcanic eruptions and erosion are two factors.
@@hansschleichert7852 Olivine does decay with time due to erosion but Olivine is fairly hard, with a mhos hardness of 6.5-7. In it's purest form, it is also called Peridot and can be faceted and used in jewelry.
Why doesn't the Mg, Fe,Si, and O continue to form olivine until one element is used up leaving nothing behind to create amphibole as the magma continues to cool?
Just did 1 through 8 before checking out 9. I know nothing about rock, and want to learn.
Just tried to add water to a rock I found and it didn't melt 😞Am curious on the physics/chemistry that would cause water to melt rocks, I assume this is with rocks that are already very hot and prevented from melting by pressure?
The water is added to the chemical structure of the sedimentary rocks in the deep ocean under high pressure as they are formed. The rock doesn't appear wet or anything like that, but you would notice a loss of mass and a change in its chemistry as you heated the water out of it. In a subduction zone, that liberated water changes the chemistry of the rocks above it, making them melt more easily.
@@TheStormpilgrim Thanks for explanation. Does this mean that water in rocks ins't truly water but rather decomposed H2 and O that chemically combine with the minerals thereby changing melting point?