Special rock

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Granodiorite I checked on line but looks different,there’s lots of yellow and silver shine around?im new in this we need answers from experience friends,thanks👍
 
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Grubstake is quite correct - granodiorite, It is not what it "looks like" that determines the rock type, but the percentage of diagnostic minerals that make it up - quartz, feldspars and micas.

Granite is a slightly less likely possibility (granodiorite and granite simply have different feldspars in them). Both are very common igneous (plutonic) rocks that make up a lot of Australia.

In this diagram showing plutonic igneous rock compositions Q= quartz, A = alkali feldspar P = Plagioclase feldspar The percentages of each mineral are written along the three sides. Plutonic rocks crystallize below the ground surface

1655956399117.png

Here is the equivalent diagram for lavas (when the magma reaches surface and flows out on the ground.

1655956732270.png
 
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Hawkear

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Certainly in the granite or granodiorite families.
The shiny bits seem to be a mica mineral, muskovite (white) or biotite (black) and the largish crystals seem to make it intermediate to a pegmatite.
A weathered or stained surface colour can be misleading and best to check a freshly broken surface for true colour.
 
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Just a granite to me, nowhere near a pegmatite. Multiple reasons - grains nowhere near large enough, pegmatites commonly contain significant muscovite (not just minor), some pegmatites contain exotic minerals like tourmaline and fluorite, pegmatite feldspars are more commonly almost all alkaline (hard to tell from a photo though). There are always rare exceptions....grain size tends to be the most diagnostic single feature.

https://www.sandatlas.org/pegmatite/
 
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I don’t now much about rocks I would like to learn but whenever I see what will catch my eye I will collect, what if I cut it?
 
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Grubstake is quite correct - granodiorite, It is not what it "looks like" that determines the rock type, but the percentage of diagnostic minerals that make it up - quartz, feldspars and micas.

Granite is a slightly less likely possibility (granodiorite and granite simply have different feldspars in them). Both are very common igneous (plutonic) rocks that make up a lot of Australia.

In this diagram showing plutonic igneous rock compositions Q= quartz, A = alkali feldspar P = Plagioclase feldspar The percentages of each mineral are written along the three sides. Plutonic rocks crystallize below the ground surface

View attachment 2335

Here is the equivalent diagram for lavas (when the magma reaches surface and flows out on the ground.

View attachment 2336
Thank you so much

Grubstake is quite correct - granodiorite, It is not what it "looks like" that determines the rock type, but the percentage of diagnostic minerals that make it up - quartz, feldspars and micas.

Granite is a slightly less likely possibility (granodiorite and granite simply have different feldspars in them). Both are very common igneous (plutonic) rocks that make up a lot of Australia.

In this diagram showing plutonic igneous rock compositions Q= quartz, A = alkali feldspar P = Plagioclase feldspar The percentages of each mineral are written along the three sides. Plutonic rocks crystallize below the ground surface

View attachment 2335

Here is the equivalent diagram for lavas (when the magma reaches surface and flows out on the ground.

Does this rocks contain gold or silver?
 
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And then what are the golden and silver flakes?
"Gold" looking flakes are usually weathered (originally black) biotite mica. "silver" flakes are usually muscovite mica.

"Many people are surprised that flakes of biotite or phlogopite mica can fool people into thinking that they are gold. This most often occurs when an inexperienced person is panning for gold and sees a bright flash in their gold pan. After chasing the tiny, highly lustrous flake, they think that it might be gold. However, slight pressure with a pin can break the flake of mica, but a tiny flake of gold will bend around the pin."



It is worth buying a x10 and x20 hand lens to look at such things. Cheap.
 
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"Gold" looking flakes are usually weathered (originally black) biotite mica. "silver" flakes are usually muscovite mica.

"Many people are surprised that flakes of biotite or phlogopite mica can fool people into thinking that they are gold. This most often occurs when an inexperienced person is panning for gold and sees a bright flash in their gold pan. After chasing the tiny, highly lustrous flake, they think that it might be gold. However, slight pressure with a pin can break the flake of mica, but a tiny flake of gold will bend around the pin."



It is worth buying a x10 and x20 hand lens to look at such things. Cheap.
I did try with knife to break it lol but nothing happened and thanks I will buy hand lens,all off this is so new to me I know nothing 🥲😉
 
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why not read my posts on how to identify minerals first - and it gives info on things like hand lenses and other cheap equipment

Search "Series on identifying minerals" under goldierocks. Start at the start - there are at least 8 of them and I did them in a logical sequence.
 
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I did try with knife to break it lol but nothing happened and thanks I will buy hand lens,all off this is so new to me I know nothing 🥲😉
try instead with a steel needle while looking under a hand lens. The mica flakes should prize apart along the layering you will see in them. Then break them with the needle. You won't break gold, it is soft and malleable (the puttey of metals)
 
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why not read my posts on how to identify minerals first - and it gives info on things like hand lenses and other cheap equipment

Search "Series on identifying minerals" under goldierocks. Start at the start - there are at least 8 of them and I did them in a logical sequence.
Actually go to this first to see what hand lens to get - get one and go back to the first in the series

Series on identifying minerals - part 3 VIEWING YOUR MINERAL
 
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try instead with a steel needle while looking under a hand lens. The mica flakes should prize apart along the layering you will see in them. Then break them with the needle. You won't break gold, it is soft and malleable (the puttey of metals)
Thanks a lot I will do that first, and then the rest,(Rodger that)👍
 
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One distinction that you need to be clear about.

1. A mineral is usually a crystalline substance with (a) a specific chemical composition and (b) a specific crystal structure, So two minerals are not the same if there chemical compositions are the same but their crystal structures are different (e.g. enargite and tennantite, both copper arsenic sulphides). Or if their crystal structures are the same but their chemical compositions are significantly different (e.g. halite and sylvite, one is sodium chloride and the other potassium chloride).

enargite and tennantire (you can see the different crystal shapes despite them having the same chemical composition, making them different minerals)



Halite and sylvite (identical crystal structures - in this case cubes, despite desite one being a sodium mineral and the other a potassium mineral (which makes them different minerals)





2. In a few cases a single mineral can grade continuously from one chemical composition to another, all with the same crystal structure (e,g, iron-rich olivine grades continuously to magnesium-rich olivine, although will usually have one specific composition at any one locality or in a particular rock sample or in a particular mineral vein). The old practice was to give different mineral names to the end members e.g. forsterite (Fo) for the magnesium olivine and fayalite (Fa) for the iron olivine, both also being called olivine. The tendency nowadays is to just refer to the mineral olivine and use a symbol to denote its relative composition as a pwercentage (eg Fo85Fa15). I find this practice confuses many people, because the old terms are still used by many people (I do it myself - I might say the olivine is fayalite or forsterite if it is dominantly magnesium or iron rch respectively). Habits of old timers, confusing for beginners.

3, A rock is typically a collection of grains of one or more different minerals. So granite is typically feldspar(s), quartz and mica(s). So to name the rock you must first identify the minerals that make it up, and sometimes you must then estimate the relative percentages of each mineral present as well. And that means that the various tests I have outlined in "Series for identifying minerals" must each be applied separately to each individual mineral in the rock before you can name the rock. So you need a hand lens to be able to see each mineral in the rock separately, and you often need to test things like its hardness and streak with a fine point like a steel needle to ensure that you are working on a mineral grain of a single type, and not averaging the properties of grains of different minerals.

Granite (an igneous rock)

Garnet-mica schist (a metamorphic rock)

Conglomerate (a sedimentary rock)


It is critical to understand these distinctions if you are not to be completely confused by the process of identifying rocks and minerals
 
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One distinction that you need to be clear about.

1. A mineral is usually a crystalline substance with (a) a specific chemical composition and (b) a specific crystal structure, So two minerals are not the same if there chemical compositions are the same but their crystal structures are different (e.g. enargite and tennantite, both copper arsenic sulphides). Or if their crystal structures are the same but their chemical compositions are significantly different (e.g. halite and sylvite, one is sodium chloride and the other potassium chloride).

enargite and tennantire (you can see the different crystal shapes despite them having the same chemical composition, making them different minerals)



Halite and sylvite (identical crystal structures - in this case cubes, despite desite one being a sodium mineral and the other a potassium mineral (which makes them different minerals)





2. In a few cases a single mineral can grade continuously from one chemical composition to another, all with the same crystal structure (e,g, iron-rich olivine grades continuously to magnesium-rich olivine, although will usually have one specific composition at any one locality or in a particular rock sample or in a particular mineral vein). The old practice was to give different mineral names to the end members e.g. forsterite (Fo) for the magnesium olivine and fayalite (Fa) for the iron olivine, both also being called olivine. The tendency nowadays is to just refer to the mineral olivine and use a symbol to denote its relative composition as a pwercentage (eg Fo85Fa15). I find this practice confuses many people, because the old terms are still used by many people (I do it myself - I might say the olivine is fayalite or forsterite if it is dominantly magnesium or iron rch respectively). Habits of old timers, confusing for beginners.

3, A rock is typically a collection of grains of one or more different minerals. So granite is typically feldspar(s), quartz and mica(s). So to name the rock you must first identify the minerals that make it up, and sometimes you must then estimate the relative percentages of each mineral present as well. And that means that the various tests I have outlined in "Series for identifying minerals" must each be applied separately to each individual mineral in the rock before you can name the rock. So you need a hand lens to be able to see each mineral in the rock separately, and you often need to test things like its hardness and streak with a fine point like a steel needle to ensure that you are working on a mineral grain of a single type, and not averaging the properties of grains of different minerals.

Granite (an igneous rock)

Garnet-mica schist (a metamorphic rock)

Conglomerate (a sedimentary rock)


It is critical to understand these distinctions if you are not to be completely confused by the process of identifying rocks and minerals
I try to find the series identifying minerals under goldierock I couldn’t (help please),and thank you for the explanation now little bit it’s clear ,I order the hand lenses 👍
 

mbasko

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