Minerals with Willsey: Olivine, Pyroxene, and Amphibole

Geology professor Shawn Willsey rounds out our survey and study of the silicate minerals by taking a close look at three common mafic (dark colored, rich in Mg and/or Fe) minerals: olivine, pyroxene, and amphibole.
Link to PDF of document I used: drive.google.com/drive/folder...
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College of Southern Idaho
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[@chrisgomez984]

Your channel is a treasure trove, I'm a second year geology student and if I fail to recognize even a tiny pyroxene in a gabro I automatically fail my petrology test (also true for any other rock-forming mineral in any other rock). And you even take the task to show how different minerals look in different types of rocks! That is awesome, I already shared this channel with my other classmates, because since our classes are short and we cannot see exactly what the teacher sees through the magnifier, we have had a lot of confusion regarding things like differentiating plagioclase from quartz in different contexts (specially when quartz is present alongside calcic feldspar). Or, for example knowing how to spot pyroxene... Again, thanks a lot

[@shawnwillsey]

Awesome. I love that these are helpful to you and other students. While the rock and mineral series is not at an upper division level, its great to hear its still useful. Good luck in your studies and classes. Soak up everything you can. Geology has brought me so much joy professionally and personally.

[@oscarmedina1303]

Thanks Shawn. Your minerals videos are really helping me learn about minerals and are helping me identify specimens I find.

[@javier090994]

Thank you for your video, I'm into mafic rocks these days. Your way of explaining, your samples, and the high quality of the camera are great! I love it.

[@helenaziegler6005]

I have a whole collection of mantle xenoliths from all over the world at home. I am obsessed with these rocks, they are so beautiful, their green color is enchanting. Here in north Italy, in the Alps, we have a locality where phlogopite-enriched peridotite can be found, the rock is simply stunning.

[@mikekilian5403]

I really enjoy these videos and love learning about minerals. Thank you.

[@emanuellandeholm5657]

Found your channel thanks to the recent volcanic unrest around Grindavik, Iceland. I must say this is a treasure trove. I'm learning so much!

[@shawnwillsey]

Awesome, thank you!

[@jadem.escarlan4294]

Sir I'm geology exploration mapper nice explanation I can learn more to your explanation about rock and minerals.thanks for your sharing:

[@MrFmiller]

Very informative, presented at a level easy for me to understand, bearing in mind I have watched every video produced by or featuring Nick Zentner. Nevertheless I am learning more and for a senior that’s important to keep my mind sharp. Thanks.

[@vibeorschmibe7319]

These videos genuinely help me out since im in a geology class and by coincidence, these videos are coming out as im in my mineral unit. id just like to say thank you for that. if i may request, when you get to the rocks, to talk about chert, jasper, and agates, since those are the rocks i most often confuse for one another

[@shawnwillsey]

I covered these a bit in the quartz video.

[@farmboypresents9977]

Awesome how many folk have watched these vids as they are posted. Rocks rock! Thanks Prof. Willsey

[@axiomrootff7223]

Thank you very much ❤

[@valoriel4464]

Excellent video. Thanks Professor 😊 looking forward to more. Best wishes from the mtns of western NC.

[@Birdman445]

Another great video. Thank you. And good introduction to Bowen reaction series. Keep them coming. Very much appreciated.

[@farmboypresents9977]

I am loving these videos. Thankyou so much. They are really helping my rock hounding and are full of the knowledge that I wanted to know but couldn't find before.

[@daveh893]

Another great presentation! Looking forward to the rocks section.

[@BlazingShackles]

great diagram at the end. puts so many concepts into perspective.

[@johnnytarponds9292]

Excellent information! Thanks again.

[@dancooper8551]

Excellent! Thanks Shawn.

[@DJBoise]

Great video, I really like this series.

[@sergiovelazquez1259]

I'vc been watching these mineral videos, very informative. Tks

[@nicholasbeck1558]

Love your videos. Thank you.

[@Rachel.4644]

Another super helpful class, Shawn. I have rocks with these minerals and can't wait to check them against my notes. I've known temperatures mattered....very interested in the next class! Thank you.

[@stg8831]

Awesome video!

[@MichaelBradley-ik9bk]

Thanks!

[@DrGeorginaCook]

Great videos thank you! Honestly I think in the UK I haven’t seen a fresh olivine 😂 as they’re so weathered. My husband did his PhD on the Lizard ophiolite so we accumulated a lot of serpentinite. In Scotland we seem to collect a lot of gneiss and I’m never quite sure exactly what I’m looking at! Oh for some crystal faces! We can access BGS maps on our phone as we travel which is great to help with ID.

[@texas2645]

Hi I love your videos because I need the basics. I used to watch nick zetner but his videos were really advanced perhaps I will watch his again after I watch yours many times over. I love geology and like to learn thanks!

[@shawnwillsey]

Nick does great work too. We each have our own styles and ways of communicating.

[@kellyjohns6612]

Correct me if I'm wrong, but I believe that the "t" in peridot is silent (pare-a-doe). And I think it's called apple green.

[@leechild4655]

I just learned too Olivine has some proportion of the two metals that make up the crystal, that being iron or magnesium so may account for its higher temp. melting point?

[@wonderfulscience427]

Thanks for another informative lesson. I really appreciate those videos:) By the way, if the extrusive basalt is being considered the product of a mafic eruption what would be the name of its felsic counterpart? And I've also been wondering if the Na-plagioclase according to the Bowen's reaction series precipitates out of the melt together with K-feldspar and both are often being refered to as an alkali feldspar group, then why do we include the albite in the plagioclase family given all the similarities with K-feldspars?

[@shawnwillsey]

Magma composition varies and we have crudely divided them into three types: mafic, intermediate, and felsic. Basalt forms when mafic magma erupts. When felsic magma erupts, it is called rhyolite. We will cover this in more depth when I do a video on igneous rocks. As for your second question, Na-plagioclase is different than K-spar but form at about the same temperatures. Alkali feldspar is the name for a group of minerals that include K-spar (like orthoclase and microcline) but also sanidine and anorthoclase. Albite is a true plagioclase feldspar based on its basic chemical formula and it also has the striations that are common in plagioclase feldspars. Hope this helps.

[@rogercotman1314]

Thanks Shawn, for another informative educational video. My question regarding the Bowen's Reaction series: Where is the location of the Magma Chamber, when the BR series is taking place?? I don't see it occurring in the Mantle, too much high heat. Therefore, when does the BR series begin when the Magma Chamber has moved into the crust?? Near the surface of the crust, or further down near the crust/mantle border area. Maybe, this topic can be clarified in a video down the road. Thanks again for your information provided.

[@shawnwillsey]

Roger, the magma chamber can be at deep or shallow crustal levels. The initial chemical make up of the magma chamber will dictate silica content (felsic, intermediate, or mafic) and also temperature. Some magmas do originate in the mantle and are therefore, high temperature, low silica mafic magmas. Maybe wait until I do an intro to igneous rocks video and see if that clarifies a bit.

[@rogercotman1314]

@@shawnwillsey Thanks Shawn, look forward to further videos on the topic. I think, this is such an important lesson in the formation of igneous rocks. Thanks again.

[@christyderycke]

Question for Shawn…immediately after a hail storm, I found rocks between my windshield and hood, which were not there before. Hail was so bad it busted two windows. Were those rocks in the hail and if so, how did they get there?

[@MountainFisher]

I've picked up a rock at Kilbourne Hole in NM near El Paso and Las Cruces and it had gem quality Peridot in it, but mostly granular, still it is only worth about $4 a carat for raw stones unless exceptional quality takes it to $7. If you want to hunt gem quality peridotite go to San Carlos Apache Indian Reservation, in southeastern Arizona. They charge you, but they have some of the best peridot in the US, but for the prices they charge you might be better off buying raw stones on eBay, but caveat emptor.

[@shawnwillsey]

I just showed a sample of peridotite from this area in my Basalt video.

[@oscarmedina1303]

Be careful taking home specimens at the Kilbourne Hole. Removing specimens is prohibited by New Mexico at that location.

[@MountainFisher]

@@oscarmedina1303 I'm talking about before they declared it a National Monument.

[@kevindorland738]

Olivine melt and flow like glass/obsidian too?

[@k.chriscaldwell4141]

Great, thanks. So, to distinguish biotite from amphibole in a rock: Biotite is more hex/round in shape and amphibole is more elongated, rod/needle like. Correct? Plus, now I know the brownish rock I thought a form of quartz is really an amphibole/hornblend.

[@shawnwillsey]

Yes. Although you don't always see biotite's hexagonal shape. A better criteria is cleavage plane. Biotite has one perfect plane and is always very shiny. Amphibole has two planes and is often needle shaped or elongate.

[@lauram9478]

❤❤

[@lauram9478]

❤

[@jennifershipp2599]

I have some lamprophyre ore from central Montana. There are green crystals in it. Are they Olivine? Or??

[@shawnwillsey]

Could be. Olivine is not an essential mineral in lamprophyre. If it's olive green, it's likely olivine. If its more green-black, it's likely pyroxene.

[@jennifershipp2599]

Thank you

[@MountainFisher]

The parabolic mirror on my reflector telescope is aluminized to 96-97% reflectivity and then coated with silicon oxide, how do they do that with quartz?

[@shawnwillsey]

I have no idea. Maybe ask a physicist?

[@kaboom4679]

CVD or chemical vapor deposition . The polished mirror is placed in a high vacuum chamber , and heat is applied to the coating material , enough to vaporize it and it then deposits on the mirror surface . Primarily they use aluminum but silicon oxide and silicon dioxide are added frequently as options for scratch resistance . Other materials can also be added to enhance performance in infrared or near infrared wavelengths . Interestingly , this process is used to enhance natural crystals , by depositing a few atoms thick layer of metal on otherwise mundane crystals , to produce a highly colored specimen , often displaying iridescence .

[@MountainFisher]

@@kaboom4679 Interesting on the crystals, did not know that. I see why they called their process a two step one, first the aluminum and then the quartz.

[@wyojohn]

Can an olivine beach eventually become a sandstone?

[@3xHermes]

👍

[@margreetanceaux3906]

I would like to live in your classroom 😘 Just kidding; recently decided to have a magnetic strip on my living room wall, specific for displaying maps.

[@garygraham6020]

Question. No olivine in sed. What about lithification of olivine rich sand? To sandstone.

[@shawnwillsey]

OIivine sand is rare but does occur such as the green sand beach on the Big Island of Hawaii. I've never seen an olivine rich sandstone. Olivine is less chemically stable than many other minerals.

[@garygraham6020]

@@shawnwillsey ok. I really appreciate the information.

[@remelynbitoon5773]

I have a pyroxene stone ..

[@deltalima6703]

Can only see the first two words of the title until I load the video. Minerals with.... Kind of dumb that I have to pick all of them to find pyroxene. Could just call it Pyroxene, olivine, amphibole: minerals with willsey And it would be *a lot* easier to find.

[@jeffrysmith8200]

Seems to me that many, if not most, of what you are calling cleavage planes are actually crystal faces.

[@addyourlighttothesumofligh7207]

Thanks!

[@shawnwillsey]

Much appreciated. Thanks for the support.