16 July 2012
Hooper Garnet Mine
Posted by Jessica Ball
Recently, I finally trekked across NY state to the Adirondacks and visited the Gore Mountain area, home of several garnet mines. Now, these aren’t like the garnets I was showing in my Bancroft photos. These are HUGE. Garnets as big as your fist. The two best places to find them are at the Gore Mountain Garnet Mine (which charges an entrance fee and by the pound for what you take out), and the Hooper Mine, which is no longer in operation BUT is also free. Being grad students, my friends and I went for the free option. (The garnets at Gore mountain are, admittedly, bigger, but there is a limit to how much rock even I am willing to drive back across the state.)
The Adirondacks are composed mainly of metamorphic rocks (gneisses and other) and a core of igneous intrusives, which are all part of a Precambrian Grenville basement similar to the one I described in my Bancroft posts. The rocks formed around a billion years ago, but the mountains themselves were uplifted only 5 million years ago – and the uplift is still ongoing. In the last hundred thousand years or so, glaciations have also sculpted the landscape, eroding and smoothing it and leaving deposits of material all over the Adirondacks dome.
The Hooper Mine opened in 1898, but closed soon after when the owner (Frank Hooper) realized he couldn’t compete with the crystals coming out of the nearby Gore Mountain Garnet Mine (apparently he went to work for the owner of Gore Mountain, too). The garnets were originally mined for abrasives, and the mines in this area are so famous that the garnet is New York’s State Gemstone. Now the Hooper Mine is on state land, which means collecting is allowed. To reach it, you pass through the grounds of the Garnet Hill Ski Lodge and resort. They get a lot a visitors for the mine, so they put together a nice little walking map and are happy to direct you there. (It’s polite to stop and let them know where you’re headed!) The hike is short, about half a mile uphill, and ends at a great outcrop of garnet-bearing amphibolite overlooking Thirteenth Lake.
View Hooper Garnet Mine in a larger map
Beautiful scenery at the top of the hill
Darn big garnets!
Not only is the outcrop full of lovely garnets, it has a ton of glacial striations!
Glacial striations in the outcrop
Glacial geomorphology and metamorphic petrology. Yum!
The mine itself is quite overgrown, but there is plenty of talus on the north slopes (and also some bouldering potential if you’re into rock climbing, although there’s a lot of loose rock and I’d be very careful).
One of the clearer slopes. Minimal rock-breaking is needed - there's so much loose material already!
The amphibolite is pretty gneissic in places
It also seems like some of the garnets have been rotated, although it's hard to determine a sense of shear.
It’s easy to spend hours here turning over (and breaking) rocks, but there’s always time for a little fun.
Nants ingonyama baghiti baba....okay, it's not a lion, but I don't know the Zulu word for rock.
If you look carefully, you can find pockets of what (might) be skarn: garnets in greenish-white masses of small crystals. These garnets are much more likely to be euhedral and unfractured; the larger garnets, which come out of the amphibolite, have tons of cleavage plains and it’s quite difficult to find intact examples.
Finding your favorite garnet takes a bit of scrambling, but it's worth it!
More of the mine
The mine is quite easy to get to, but be sure to bring sturdy boots, gloves, serious rock hammers, and plenty of bug spray and sunscreen (and snacks!) If you’re tired of roasting yourself in the mine, the Hudson River is also nearby and there seem to be a lot of rafting companies running trips.
Jessica Ball is a volcanologist at the U.S. Geological Survey, researching volcanic hydrothermal systems and stability, and doing science communication for the California Volcano Observatory. She previously worked at the Geological Society of America's Washington DC Policy Office, learning about the intersection of Earth science and legislative affairs. Her Mendenhall postdoc and PhD focused on how water affects the stability of volcanoes, and involved both field investigations and numerical modeling applications. Her blogging covers a range of topics, from her experiences in academic geosciences to science outreach and communication to her field and lab work in volcanology.
It looks like you had a fun rockhounding trip!! Garnets the size of your fist- I haven’t seen that before. Just be careful not to slip on that loose rock if you ever scramble around those boulders. It is amazing that we can see the results of processes taking millions of years in the rocks all around us- mountains uplifting, glaciers advancing and retreating, rocks eroding into dust…
Reminds me of when I did my mapping field trip in Southern Norway as an undergrad back in 1981… the area was precambrian amphibolite facies as well.
Plus there was the one old quarry with Garnet-bearing peridotite… these things were huge, I remember our lecturer referring to them as “Garnets as big as your fist – and sometimes your head!”. Would love to return there, but upper NY State seems a bit more feasible – thanks for the idea!
I shot a video collecting garnets at Hooper Mine about a month ago…got a pretty big one in it https://www.youtube.com/watch?v=7niihtVBG3g
Just went to the mine today and am reading up nthe geology of it now. Great site!!! BTW… to be specific, rock collecting on State Land is NOT allowed, however unenforced it is 😉
Visited the old quarry today. I’m a retired research/exploration geologist in mining industry out west: AZ, NM, NV, MT, ID, CA, CO, Canada, Mexico; Looked for Cu, Mo, Au, Lanthanides, Nb, Ta, Y, Zr. Really neat metamorphic rock and glacial features at the mine. I’m also spending time catching up on Adirondack Mtns geology and Grenville Orogeny on my visit back east.
What evidence is there for 5ma tectonics in the Adirondacks? As far as I know there are no young cooling ages on thermochron samples or mapped active faults in the area? There’s some argument that a few hundred meters of relief was created along the NE US during the late cenozoic from epeirognenic tectonics (gentle tilting over long wavelengths in response to changes in farallon slab subduction underneath the craton), but is it a common view that there is very significant tectonics in the Adirondacks, specifically at 5 ma? The mine looks cool, and I’m planning on taking some graduate students up here for a field trip, but the relief in this region has always kind of puzzled me. Thanks for posting!
Hmm…I haven’t been able to find the references I used to write the post. It’s quite an old one, so it’s possible the ages have changed from when I wrote it!
You state that anyone can go and dig at Hooper for free. Does the ski lodge charge to go through their grounds? Are there signs to get there? What equipment do you suggest? Husband and I are interested in doing long song mini g for a garnet for a ring. Do you know if the quality of the gemstones are good?
Thank you for your help
Arline
You state that anyone can go and dig at Hooper for free. Does the ski lodge charge to go through their grounds? Are there signs to get there? What equipment do you suggest? Husband and I are interested in doing long song mini g for a garnet for a ring. Do you know if the quality of the gemstones are good? It’s for our grand daughter’s graduation in area years.
Thank you for your help
Arline
The lodge didn’t charge when I was there, no. They have a marked trail showing you how to get to the old mine, which is quite grown over but still reasonably accessible. The garnets are quite large but not great quality, although if you’re looking to find a piece for a ring you might manage. I would bring a sledgehammer to break up rubble that’s already on the ground and something sturdy to carry your finds in (the matrix rock is quite heavy and hard and will take a fair bit of breaking).
They do not charge. Go up to Garnet Hill lodge and have dinner and a drink after your trek or before as they offer hikes and tours if you request. Ski lodge you turn right, if you go left you end at the lodge, beautiful views.
On the way up 13th Lake Road you can stop at Garnet Hill Studio, she can give you a wealth of info.