When you think of native gold mineral, you generally envision nuggets of gold. Flakes floating through a river… Being six years old and panning in a sand pit at some old timey festival.
That vision adequately describes gold found in alluvial deposits… basically, soil along rivers. It’s mined by placer mining (open pit mining, surface excavation) which includes the good ol panning for gold.
Other sources of gold are ores: rocks with deposits of gold in it at about 1-5 parts per million in open-pit mines and 3 ppm in underground mines.
Because ore grades of 30 ppm are usually needed before gold is visible to the naked eye, in most gold mines the gold is invisible.
To extract gold from these ores, the miners dislodge the rock and soil. Sodium cyanide is then used to extract the gold and the rest is considered waste.
Gold Mining Impacts (if not properly mitigated)
I’m not an expert in the geology or mining technical info but here’s what I’ve gathered:
Gold is found in ores containing sulfides (such as pyrite, an iron sulfide). These rocks will produce sulfuric acid when exposed to air and water. The accepted practice is to protect these stockpiles so that they don’t interfere with the natural environment. But in the case that they aren’t…the acid mine drainage will dissolve metals like arsenic and mercury and release more contaminants. (Fun fact! Roman-era mines are still releasing this today!)
And that… brings us up to all the problems:
- Metals are released into the environment
- Metals seep into the ground
- Contaminate the groundwater
- Run off into the waterways (75% of the rivers in Ghana are polluted due to this activity. Yuck!)
- Difficult and costly to extract the metals out
- Mercury is released airborne
- It accumulates in rivers, lakes, and ultimately fish
- Then transferred to your dinner (and bear’s dinners? I dunno, I’m not a biologist)
- Deforestation (in order to mine the land)
- Accelerates erosion
- Creates bad water quality in the streams
- Negative impacts for downstream ecosystems
- Cyanide spills = bad!!!
- Compromises to wildlife habitat
- Disturbance to indigenous cultures
- Scouring of the landscape
- Reduced ability to farm
- And on, and on, and on.
Golden Field Trip
On the featured image at the top of this post, you can see some of the gold mining precipitate on the river rocks. I traveled to see this with a geologist and chemist (shout out to two amazing loving people, Bobby and Amanda!) and we thought it was ironic that mining pollution was a tourist attraction. Not that it stopped us from going to see it too!
Bobby even washed his hands off in the water…Amanda and I face-palmed.
Chinkuashih is an important gold/copper producing area in Taiwan near the port of Keelung (check out my youtube videos on the Keelung night market! Part 1 and Part 2). There are multiple mines here with Jiufen (video of this amazing town) being one of them. In 1972 the production high was at 30,000 ounces of gold.
Geologically, this ore is formed in breccia pipes in dacites (igneous rocks) and calcareous sandstones (sedimentary rocks). These deposits are formed at 240C to 300C with cooling brought about by the influx of meteoric waters. Just reading that sentence I think “Science is SO cool”!!!
Well, what are the safe ways to mine?
I admit that I’m not well versed in the mining sphere. Because I do water engineering what I know is from that background. Within my company there are geochemistry modelers who work mostly on projects where they predict things like acid rock drainage for the purposes of risk assessment. They (or, more accurately, the entry-level geologists) do field visits to perform leaching tests and petrographic analyses. From those results they develop a mixing model using a program developed by the USGS called PREEQC (pronounced ‘freak’) to do a bunch of calculations on aqueous (water) models. These may take the form of reactive transport models (as in, transport of the heavy metals into the environment).
At my company, we also employ many environmental engineers–these gurus know about permitting, compliance, and environmental protection. They do the nuts and bolts of interfacing between the client and the regulatory agency. They’ll send off quarterly reports, do any sampling required, and track contamination plumes using CAD.
Small Scale Gold Production
Small scale production, known as “galamsey” in Ghana, can lead to polluted waterways. Environmentally, it’s similar to that mentioned above…but there’s more to the problem. About 20 million people worldwide are involved with which produces 20% of the gold mined in the world. These untrained, poor workers are in unsafe conditions exposed to harmful toxins.
Buying Retail Gold?
A pledge was launched in 2004 called No Dirty Gold and is upheld by the “golden rules”. Don’t you just love nerd puns?
Anyway…. these rules encourage the mining industry to respect the environment and gold workers (working conditions, mercury poisoning). Different companies which stand behind this pledge can be trusted to buy responsibly. Check out the list of retailers at this website. It includes some familiar names like Tiffany & Co, Target, and Helzberg Diamonds.
How do I protect the waterways without a degree in geology or geochemistry?
We bring awareness to it. We millenials share and retweet and repost. This helps in small ways.
There are also bigger ways to help. I am talking about being politically active.
I know us nerds don’t exactly like talking to people, but we need to bring forth a conversation about it with our representatives so that we can inspire legislation. Talking to representatives is not always the most fun part of environmental engineering, but it’s necessary. We wouldn’t be living with such clean waters and airs in the U.S. if courageous, beautiful people hadn’t done this in the past. It’s our responsibility to do it for the future.
And if talking to your reps is your thing?
Get involved! Most of the time, our careers are not what we learn in classes. There’s potential to take the fun geology classes (going to field camp, learning about thin sections and mohr’s circles) and then using that background for change. Encouraging the social and political change through lobbying and… Heck, maybe one day you will be our representative! That’s not a “dream big” scenario–you have the potential. It’s realistic and it’s attainable if that’s what you want.
If you’re looking for a community to talk about this stuff with, check out a group that I run on Facebook! https://www.facebook.com/groups/enginist/
Reading: When Broken Glass Floats by Chanrithy Him. I picked this book up in Hoi An, Vietnam during my travels. It’s about a girl growing up under the Khmer Rouge. It’s a true story and heartbreaking every step of the way. It’s EXACTLY what I need in my life right now. When my problems start to feel big to me, I can sit in my cozy home with my kitties around me and read about real problems, real struggles. It’s the perspective I need. It’s inspiring seeing the persistance of others to make it through abnormally, inhumanely tough times.
Working: Operations & Maintenance manuals for wells along a railroad track. I’ve been working on these for a bit now which you may have noticed if you’ve been following me on instagram or twitter. I’ve had some shake-ups at work recently but I’m waiting for the dust to settle before I tell you about it. Coming soon! Dun dun DUUUNNNN!
Listening: S-Town. Downright good storytelling. If you liked the way Sarah Koenig told Serial, you’ll certainly like this one too.
Folinsbee, R. E., Kirkland, K., Nekolaichuk, A., & Smejkal, V. (1972). Chinkuashih; a gold-pyrite-enargite-barite hydrothermal deposit in Taiwan. Geol. Soc. Am. Mem, 135, 323-335.
Yang, J., & Meyer, H. O. (1982) Chinkuashih Ore Deposits, Taiwan. Proceding of the Geological Society of China. 25:88-101