Light lavender rock with mica crystals

[velodromed]

  Texas river rock, possibly Rio grande valley
  Very light and even lavender color. It has small, square mica or quartz looking crystals through out and a couple of blood red veins running through it. 
  Larger grained then chert but smaller then quart. It seems to be made of very small and consistent silica grains.
  Very hard and absorbs shock. It took multiple hits from the 2lb sledge to break. It breaks off in large, even planes (I think it’s called), mostly triangular pie shaped. It did not spark or give off that chert/flint smell (if that makes sense).

The kid and I found this at a nearby rock yard yesterday. It is striking in the sun, the lavender brightens and imbedded crystals sparkle. The inside surface feels like 200 grit sand paper. It’s unlike anything we’ve run across and I can’t find anything similar online. Lepidolite Keeps coming up but it doesn’t seem the same. I broke off some pieces to tumble in hopes it’ll take a shine. Please let me know if y’all have any idea what it is. Many thanks and Happy Friday!!

[hummingbirdstones]

Maybe it's Aventurine?  It would be helpful to know how hard the rock is.


geology.com/gemstones/aventurine/

[velodromed]

Mar 31, 2023 9:13:13 GMT -5 hummingbirdstones said:

Maybe it's Aventurine?  It would be helpful to know how hard the rock is.


geology.com/gemstones/aventurine/

Possibly around 5 on the Mohs? A penny doesn’t scratch it but a screwdriver easily can. It’s more resilient than hard I think since it doesn’t shatter under the hammer. The edges are not sharp like Jasper and the thin extreme edge of the triangular break can be crumbled off slightly. Maybe it’s between Microcrystalline and macrocrystalline? Can’t see the grains with the naked eye but can a bit with a 30 times magnifying glass.

[rmf]

looks like a rhyolite

[velodromed]

Mar 31, 2023 10:42:14 GMT -5 rmf said:

looks like a rhyolite

Nice thanks! It looks more like pink rhyolite than anything else I’ve found so far…

[Peruano]

Garnet Schist ?

[Son Of Beach]

Nice find, thanks for showing it off.

Really interesting.

[velodromed]

Thank you everyone, it is rhyolite. I started looking at many of the rocks we’ve broken and there’s a lot of it around here of different colors, like reds, grays, browns etc…and now lavender. I’ve learned so much researching this rock we’ve always wondered about. My kid calls the black version ‘space rock’. Now I’m wondering if it tumbles well, the red veins through the lavender rock will look really good if it does.

[velodromed]

I’ve changed my mind on this rock. Putting the color aside, the grain size, toughness and outer shell mimic the quartzite I’ve been finding around here. So perhaps that’s what it is, lavender quartzite. That’s what I’m going with lol.

[fuss]

Rhyolite, with probably Quartz phenocrysts.

[velodromed]

Aug 24, 2023 19:01:16 GMT -5 fuss said:

Rhyolite, with probably Quartz phenocrysts.

That’s what I originally thought until I researched it further. It’s harder than rhyolite and took a hardened steel drill bit to scratch it. Rhyolite is a 6 on the mohs. It has course grain that’s not shiny, Rhyolite has very fine grain and often a slight glassy appearance. This rock does not crumble or chip when broken, just breaks off in smooth, large, often triangular chunks. All the rhyolite I’ve seen is more rough when it breaks, with small peaks all over. I’m not sure it qualifies as Porphyritic, so phenocrysts may be the wrong description of the crystals. The only thing that throws things off are the imbedded crystals and iron oxide vein. I haven’t seen features like that in all the other quartzite I find. Yeah, I guess I’m still vacillating between one and the other. Honestly I wish it was rhyolite as I haven’t found any of that yet. Talk about paralysis from analysis.
To be continued lol…