[Brushbuffalo]

"Could you start a 'name that rock' thread?" Ask, and you shall receive. [ edit: modified to "What's this rock? What's that landform?"] Due to several requests, here goes. Although it sometimes can be very difficult to identify materials from just pictures without a sample in hand, and often also an extended visit to a site and the surroundings, let's give it a whirl. Send clear pictures of rocks to this thread if you'd like me to give a shot at identifying for you and our audience. Ideally, images should be as close-up as you can do, with something in the picture for scale (key, Swiss Army knife, etc.). Also it is helpful to include a photo with a more general view of the outcrop. - Please try to show "fresh" rock, not stained, excessively weathered, dirty, or lichen-covered surfaces. - "Bedrock" is still attached, "float" is loose rock. Either is fine. Please also include if possible: -Location, being as specific in your description as you can. My credentials: Banged with a rock hammer and carried samples as a strapping young USGS field assistant for geologic 'rock stars' ( ouch! )Rowland Tabor, Dwight Crowder, and other outstanding geologists in the North Cascades. B.S. in Geology(1970) Western Washington State College M.S. in Geology (1977) Western Washington University 43 years teaching college geology, meteorology, and oceanography Professor (emeritus), Whatcom Community College, Bellingham. Have had the privilege of working with thousands of students of all ages, including a freshman grandchild of one of my early students. How time flies. I've seen not only a lot of rocks but also structures and landforms in the Cascades and elsewhere! You can ask questions about those things, too, without fear of the dreaded ! I especially like weird oddities. Sometimes they are simple to explain, but once in a while.... ! Keeps the ol' gray matter alive... -

[contour5]

I'm curious about these crystals I found.

Crystals-1

Crystals-2

They were exposed on the uphill side of a 3' boulder in the talus apron at the base of Alta Mtn. (right below the lens flare in this picture)

Here's some bedrock peeking out a couple hundred feet above the tarn:

There were also boulders of conglomerate laying around:

Conglomerate

I didn't get a good shot of the crystal boulder, but you can see some of it here:

[DIYSteve]

Cool. Very gneiss of you

[Brushbuffalo]

Thanks for getting this started, contour 5! You included lots of good images, including close-ups. Perfect! Crystals-1 is quartz (#2 in continental crustal abundance) with feldspar (#1) in upper right and in left 1/3 of image. Crystals-2 is all quartz, and good euhedral (good external form) crystals! The 'conglomerate' is breccia as indicated by the angular nature of the particles. I'm calling it volcanic breccia rather than sedimentary breccia. On the geologic map of the North Cascade Range, Alta Mountain is mapped as "Tcao", which is "volcanic and sedimentary rocks of Ohanapecosh episode ( Oligocene). Remnants of a series of volcanoes that erupted from about 34 to 30 million years ago." (and Steve, thanks for the gneiss comment)

[Kim Brown]

Be still, my heart! Yer talkin' purty.

[Malachai Constant]

Quartz crystals, the rock is breccia as the fragments are sharp cornered conglomerates are usually rounded cobbles cemented together.

[radka]

[Brushbuffalo]

edited Greenish quartz is uncommon and some isn't even naturally- occurring. The partially fake kind is called aqua aura quartz and interestingly, the color is due to traces of gold. Pretty stuff, even if slightly faux. But the gold in it is not concentrated as pure gold such as gold nuggets in vein quartz. Aqua aura quartz has a cultish aspect.. In fact, it is not a natural color! So what you saw on Blackcap might be prasiolite. I've neither seen it nor heard of it in the Cascades, but that means very little per se. Not even Rowland Tabor has seen all the rocks, or even Fred B, Fay, or John R! Edited again on Nov. 24: green mineral is most likely fluorite. Thanks, GC99.

[Kim Brown]

[Brushbuffalo]

[Kim Brown]

Sorta like the tide is coming in. Or going out. So yeah, great thread. I have a mystery rock (that I did keep - it's that cool) I'll post a portrait of it tonight!

[Jake Robinson]

Not really a rock ID question, but any idea how these parallel lines could have formed? This was taken on the summit of Mount Mystery in the Olympics.

Mystery rock feature

[moonspots]

[Brushbuffalo]

[Brushbuffalo]