Odd shaped quartz habit on mica schist?

[fuss]

I found this glacially tumbled green mica schist/gneiss rock in the woods of my backyard in SE WI. On one side of it has a patch of quartz formations that have a "stacked" and stepped" appearance (not sure if that's a proper description) to them. The crystals have a hardness of 7-8 range. They are very small and cannot be seen unless magnified (the stacked ones).

Also trying to figure out if some of the mica is fuchsite variety? the rock seems to have varying colors of mica from black to greenish. the rock surface has a hardness of 2-3 on the exterior(green) as well as interior(black) on a freshly chipped section. Streak is white and black/dark green mixed powder grains that do not react to acid.

I know this is not a special rock, just interesting to me and trying to understand what it is made up of. Thx.

 

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[stdenis_jd]

That gneiss is rich in iron, the green isn't fuschite it's probably an amphibole such as actinolite, ferro-actinolite or tremolite

 

[fuss]

What a coincidence, I was just reading about actinolite on the Wisconsin geological mineral page. Seems like the hardness is quite a bit off though to be it. Any thoughts on the first image of the quartz stdenis?

That gneiss is rich in iron, the green isn't fuschite it's probably an amphibole such as actinolite, ferro-actinolite or tremolite

 

[stdenis_jd]

as far as the quartz, just seems like quartz to me. Anything specific that seems off about it?

Amphibole & pyroxene minerals cover a broad spectrum as rock forming minerals. Could be many different things, could be a mica colored green by chlorite too...really it's kind of an educated guessing game without microscopic or chemical analysis

 

[fuss]

as far as the quartz, just seems like quartz to me. Anything specific that seems off about it?

I circled the areas of quartz that have a stacked or stepped appearance, I have not seen this before, but then again I have only been looking at rocks for 6 months so maybe this is not an uncommon habit? you may need to zoom all the way in to see it.

 

[stdenis_jd]

oh ok, I see what you mean - those are either the typical striations you will see on well formed quartz crystals (those striations don't show on the terminations) or just as you said, stacked quartz trigons. pretty cool

 

[IAMZIM]

I circled the areas of quartz that have a stacked or stepped appearance, I have not seen this before, but then again I have only been looking at rocks for 6 months so maybe this is not an uncommon habit? you may need to zoom all the way in to see it.

View attachment 1689595

As far as being uncommon, I would say that would depend on the area. Where I am, I see that habit in quartz as being very common where I dig. We get alot of cathedral and skeletal quartz here that looks very similar to those "trigons" as stdenis_jd calls it. It's cool that you noticed those small details in your rock!

 

[fuss]

Thx for taking a closer look stdenis_jd.

 

[fuss]

Thx, I look over some rocks with a loupe to see if there is anything interesting going on.

As far as being uncommon, I would say that would depend on the area. Where I am, I see that habit in quartz as being very common where I dig. We get alot of cathedral and skeletal quartz here that looks very similar to those "trigons" as stdenis_jd calls it. It's cool that you noticed those small details in your rock!