Interesting agate with inclusions

[mamabear]

A friend gave this to me several yrs ago. I have always thought it was agate. Am I right? & what could these mass inclusions?

 

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[Jim in Idaho]

That's a really nice dendritic agate, Mama. The inclusions are dendrites.
Jim

 

[mamabear]

Thanks Jim. I have been going through my rocks, & found this one. It will go in my show case, front line. Didn't know sorting my rocks could be so much fun.

 

[DDancer]

Looks like rhyolite inclusions in that agate Mama. Nice stuff Not sure if they qualify as dentrites as they are crystals in and of themselves and dentrites are also crystal formations usually of a metallic nature like copper, silver and manganese *moss agates*. I've always found it fascinating to find inclusions of other minerals inside of host materials

 

[Jim in Idaho]

Definition of dendrite:
A:a branching treelike figure produced on or in a mineral by a foreign mineral; also : the mineral so marked
B: a branching figure or marking, resembling moss or a shrub or tree in form, found on or in certain stones or minerals due to the presence of a foreign material.
C: A mineral crystallizing in another mineral in the form of a branching or treelike mark.
I didn't find anything suggesting that dendrites have to be metal.
Jim

 

[curious kat]

What ever it is mama...it's pretty & interesting.

 

[AuSomeness]

That is a very cool rock specimen! It has the appearance of pine needles trapped inside! Very neat!

 

[CaliRockhound]

What you have mamabear is called rutilated quartz. the golden needles are titanium and they formed first. the quartz formed later.

 

[DDancer]

True enough Jim~ I just have it set in my mind in a different manner and did not mean to sound contrary. To many chemistry experiments as a kid precipitating silver and copper from solutions. Just goes to show how I view things at times.

 

[Jim in Idaho]

No big deal DD...I enjoy your knowledge. If that is titanium, as Calirockhound says, that would be a really neat specimen. I'm gpoing to have to look up "rutilated" quartz. Aaaah...rutilated quartz is quartz containing crystals of rutile. Rutile is titanium dioxide. Usually reddish-brown in color. The interior crystals can have an adamantine luster. So, it can be both rutilated and dendritic at the same time, though "rutilated" is more accurate and descriptive.
Jim

 

[BurntBear]

Hey guys, I've always associated "rutilated quartz" as just that, pure quartz with rutile. I have some. I've never heard of it being called "rutilated quartz" in microcrystalline or cryptocrystalline formations. I'm aware that rutile can form in each type, but I've always heard it called by a different name when applied to agates. Am I missing something? Thanks.

 

[Jim in Idaho]

No, probably not (missing anything). There are many confusing names in geology. Some of them are local, some have been changed for more descriptive names. That practice is ongoing, so there's always a little confusion (and room for discussion....LOL). Best practice, when something isn't clear, is "look it up".
Jim

 

[gunsil]

I do not think it is rutilated quartz although there is a similarity. It is sagenite sprays or needles in agate, often found down Mexico way.