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In this video, Rock Papa identifies a rock found in Great Smoky Mountains National Park (Elkmont Campground, Tennessee side) using the free Rock Image ID Key web app and the RockD geologic map app. The rock shows a fine gray matrix with embedded white feldspar and a bit of blue quartz — and those rough-edged grains tell an important story.

By combining field observations with location-based geology, we conclude this rock is best described as greywacke / meta-greywacke — closely related to the Elkmont Sandstone shown on RockD.

🪨 What You’ll See in the Rock

Fine-grained gray matrix

Visible feldspar grains (white)

Visible blue quartz

Grains are rough-edged, not rounded (key clue!)

Texture consistent with turbidite sandstone / greywacke-style sandstone

🔍 Identification Process

In this video, we:

Use RockD to pinpoint the collection location at Elkmont Campground

Learn the bedrock unit is labeled Elkmont Sandstone

Compare the sample to multiple rock categories in the Rock Image ID Key

Rule out igneous look-alikes (like dacite) based on geologic setting

Identify the best match as greywacke / meta-greywacke

Explain why “Elkmont Sandstone” and “greywacke” can refer to nearly the same rock, depending on grain/pebble size and metamorphic overprint

🌎 What Is Greywacke / Meta-Greywacke?

Greywacke is a sandstone that commonly forms from turbidity currents (underwater sediment flows). It often contains a muddy matrix and angular grains of quartz and feldspar. In mountain belts, it may be mildly metamorphosed into meta-greywacke.

And here’s the neat part:
Greywacke is specifically listed as being found in Great Smoky Mountains National Park — a nice “smoking gun” match for this location-based ID.

🛠️ Tools Used

Rock Image ID Key (free web app)
👉 https://rockpapa.github.io/Rock-Image
...

RockD app (Cornell University geologic map)

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This is Rock Papa wishing you happy rock hunting 🪨🤠