September 17, 2012
Monday Geology Picture(s): Garnet Sands in Nome, Alaska
Posted by Evelyn Mervine
Gold-bearing garnet sands on Western Beach in Nome, Alaska, Summer 2012.
Above is a gorgeous beach sand picture for this week’s Monday Geology Picture. I took this picture a few weeks ago in Nome, Alaska after a summer storm. The beaches of Nome are rich in red garnet grains. The beaches of Nome are also very rich in grains of gold, and you can bet that if you pan some of the red garnet sand along the Nome beaches, you will find dozens of small flakes of gold. If you pan some of the more gravely beach material, you may even find yourself a gold nugget!
The beaches of Nome are always a rich red color, but after a storm the beaches look particularly red. This is because the storm waves remove some of the lighter beach sand grains (quartz and such) while leaving behind a lag of beautiful bright red garnet… and dark heavy minerals… and gold!
Here are two more pictures of the red garnet beach sands in Nome:
More red garnet sands along Western Beach in Nome, Alaska, Summer 2012.
More red garnet sands– and beach cobbles– along Western Beach in Nome, Alaska, Summer 2012.
And here’s proof that if you pan some garnet sand from Nome, you will find gold:
Panned garnet sands from Western Beach in Nome, Alaska, Summer 2012. Note all the little gold glakes on the left side of the pan. Click to enlarge picture.
Gold panning is a gravity concentration process in which a large plastic pan and water are used to separate minerals according to their density. Gold is a very dense material (pure gold has a density of ~19.3 g / cm3), so gold will be sink to the bottom of the pan while much lighter sand grains are washed off during the panning process. Panning first removes the lightest sand grains such as quartz (density of ~2.7 g / cm3) and muscovite (density of ~2.8 g / cm3) and leaves behind heavier grains such as garnet (density of ~3 to 4 g / cm3), magnetite (density of ~5.2 g / cm3), and ilmenite (density of ~4.7 g / cm3). Eventually, the panning process leaves behind a dark-colored, heavy mineral concentrate that is rich in gold!
Here I am with just such a concentrate from Western Beach in Nome:
Me, with a gold pan and a bag of gold-bearing heavy mineral concentrate in Nome, Alaska, Summer 2012.
That’s an old gold dredge in the background of the above photo; I’ll write about the some of Nome’s old dredges in another post.
Wow! I didn’t know there was such a thing as garnet sands. I’d like to see that for myself someday. Very neato!
Garnet sands along Napatree point, Watch Hill, RI have no gold. I’ve checked.
That’s too bad :-).
What a wonderful distraction from all the political news of the day! This article was so pleasant that I shall book mark this blog and try to return to it for daily therapy by means of geology.
Thanks so much, Fred! I hope you continue to enjoy my blog posts.
Yes it is interesting since gold is commonly associated with hydrothermal igneous rocks, sulfides, pegmatites, quartz diorite, etc. Association of gold with metamorphic rocks seems to be unusual. Thanks for sharing your rare findings. I included a short synopsis involving garnet-rich sand deposits found at Montauk Point, Long Island, NY for general information. I hope you find this pertinent to your topic.
2006 Philadelphia Annual Meeting (22–25 October 2006)
Paper No. 26-8
Presentation Time: 8:00 AM-12:00 PM
PROVENANCE OF A GARNET-RICH BEACH PLACER DEPOSIT, MONTAUK POINT, LONG ISLAND, NY
KHANDAKER, Nazrul I., SCHLEIFER, Stanley, ALI, Zarine, and JEMILUGBA, Olalekan M., Natural Sciences Department, York College of CUNY, 94-20 Guy R. Brewer Blvd, Jamaica, NY 11451, [email protected]
Garnet and magnetite rich sand, also enriched in monazite and zircon, has been observed and sampled near Montauk Point, Long Island. The sediment is derived from the glacial till and stratified drift of the Ronkonkoma Moraine by mechanical weathering and erosion due to wave action at Montauk Point, the headland on the eastern tip of Long Island. Sand sized sediment is moved westward along the southern shore of Long Island by longshore transport. The garnet and magnetite components of this sediment are significantly denser than the quartzo-feldspathic components. This allows for hydraulic segregation of these components, by wave action, producing a placer deposit of sand enriched in garnet and magnetite. Although the proximal source of the sediment is obviously the Ronkonkoma Moraine, the ultimate source remains to be determined. The chemical composition of selected minerals in the placer deposit is compared that of the same minerals in the rocks of the glacial till. Preliminary results indicate similar garnet compositions, for the most part, in the placer deposit and the rocks of the glacial till. However the possibility of a mixed provenance for some of the beach sand minerals exists. For example, stratified drift in the Montauk Point area may, in part, be derived from the Harbor Hill Moraine as well as from the Ronkonkoma Moraine. Rocks of the glacial till may come from different source areas as well.
2006 Philadelphia Annual Meeting (22–25 October 2006)
General Information for this Meeting
Session No. 26–Booth# 106
An Early Involvement of Undergraduates and K7–12 Students in Geological and Environmental Research (Posters)
Pennsylvania Convention Center: Exhibit Hall C
8:00 AM-12:00 PM, Sunday, 22 October 2006
Geological Society of America Abstracts with Programs, Vol. 38, No. 7, p. 77
Interesting abstract– thanks for sharing!
Ooooohhh I would love some of that for my incense burner.
I first met a garnet placer walking along the shore of a Scottish highland loch many years ago. Though I hadn’t thought of associating them with gold placers.
I’ll have to go and spend some time at Kildonan with my frying pan!
Really interesting text and photos about the the Nome garnetsand,
I am working with Goldprospecting here in Scandinavia and have seen similar but much smaller garnetbeaches here then at Nome. Very interesting sight under the microscope.
I like good people and have a good attitude and serve them as their mother and I pray I wish my mother were alive.
I like good people and have a good attitude and serve them as their mother and I pray I wish my mother were alive
My husband and I were in Nome from Aug 3rd to the 10th this summer (2013)
and got lots of “concentrates”. However they are next to impossible to separate from the black sand. We don’t want to use the earth magnets, mercury, etc. etc. Suggestions? Love your pix. Thanks
Probably the first thing to do would be to check – with hand lens or binocular microscope – whether there is enough gold to be worth the effort. What your ultimate aims are will be a major imput to this – are you collecting to make memento jewllery, or for geological specimens, or what.
Quantity is also an issue – you’d use different techniques for 100g of concentrate than for 100kg.
You’re wise to avoid mercury – it’s expensive, hard to obtain, a cumulative toxin to users and it’s extremely difficult to control well enough to not be an environmental toxin.
Probably your best first step would be to try a density separation step, to “float off” the low density minerals. You effectively do this in your panning stage, but it’s more controlled in the lab. You will need to effectively build yourself a laboratory (a utility room with a sink, separate from food preparation areas would suffice).
Wikipedia lists a selection of “heavy liquids” ; most of these are a combination of expensive, poisonsous and volatile (to some degree), and many of them I’ve refused to work with in the past, as they are (or are structurally related to) known cumulative poisons. All of the halogenated hydrocarbons I’d expect to be no safer than chloroform, which is no longer used as a routine anaesthetic because of it’s cumulative toxicity. Similarly, the salts of heavy metals (indium iodide, barium mercuric iodide) I’d avoid on general principles. (It’s possibly that you’ve more laboratory experience than I have, but unlikely.)
I don’t know sodium polytungstate ; it does sound interesting for your task, but with a density of only 3.1, it’s only going to “float off” quartz and most feldspars. A lot of garnet, for example, would sink and remain with your concentrate. Whether this is worth the effort is for you to batch test.
Zinc bromide, as a saturated solution, has a density of up to ~2.5 (rather temperature dependent), but it relatively low toxicity (3-5g lethal dose). I’ve never used it, but did source materials for using it once (the client decided to not use that test – he’d hated using such materials when he was in the field, and decided that the data wasn’t worth the risk).
Zinc iodide solution can theoretically get up to a density of ~2.8, and would have similar toxicity issues to zinc bromide (i.e. you could kill yourself, but you’d have to work hard at doing it), so that might be worth considering too. But again, a lot of garnet would stay in the “concentrate”.
If the above sounds discouraging, it should be. Separating such mixtures is actually very difficult. The only person I know who traded in gold ore (from amateur collectors), bribed a friend in the local university to do assays for him (to determine how much to pay for each batch of concentrate from each collector ; the university got the approximate location and the analysis for thier records), then batched up the concentrates and sold them to a metals trader to go into the conventional processing stream.
I might consider embarking on such a project, but precisely because it is difficult. And I’ve been building and operating industrial laboratories for most of my life.
THANK YOU FOR SUCH AN EXTENSIVE, TIME-CONSUMING, COMPLETE, INFORMATIVE, ANSWER THAT COMPLETELY BOGGLES MY MIND. I DO NOT KNOW ABOUT ANY OF THE PROCEDURES YOU ARE MENTIONING. I know that GPAA uses the shaker table to separate a lot of the fine flour gold. We have about two quarts of concentrates from the Nome beach sands, having gone up to Nome with the GPAA for a week this summer. I have been using my Gold Magic to separate the gold, then panning about three teaspoons a night and getting some VERY LITTLE GRAINS. I just wonder how much microscopic gold there is in the left over concentrates as I have been told there is a lot. Where do you get the microscopes you are talking about and are they expensive? Honestly you don’t have to answer this extensive entry because you have answered so much already so THANK YOU AGAIN!!!!!
I don’t know who GPAA are, nor what a “Gold Magic” is. I’m guessing a geological club of some sort, and a panning tool? Whatever.
Microscopes : I use a variety of scopes at work routinely. Anything with stereo vision (i.e. two eyepieces, leading to two objective lenses) ; magnification up to about 30-40 diameters. That’s what I need for work, and is what I got for home too (the burglars had it ; I haven’t replaced it). I looked around carefully and found a tool that suited me for about GBP250 (USD 350 ; not sure about Canadian $). That was an excellent Russian design (brand Zenith ; model MBC-2). But it’s not been available new for years now, as far as I can tell. Sad, because it was an excellent machine.
I was recently advising our storesman about repairs to our existing fleet of 20 or so microscopes, and we’ll probably be buying a couple of new Meiji scopes ; model SM-5 or SM-10 (I think ; I wrote the report and promptly forgot it ; it’s now 7000km away), costing about GBP 500-600 each. Fit for the purposes we need.
You can probably pick up as-good, or better, at much better prices from ebaY. I sometimes browse and consider getting a scope again .. .then I consider how much the wife would hit me if I did that.
did you see any lights in the skys around that area
Walking with my grandson on Southeastern CT shore (Stonington) and he spotted the “line” of red. Papa took out the hand lens and sure enough…. garnet.