Field trip to the Herkimer diamond mine

Herkimer, NY, USA

This was a day trip of the Union College Geology Club to the Herkimer Diamond Mine and KOA campground located north of Herkimer, NY. Herkimer diamonds are the local name for doubly-terminated quartz crystals that grew in vugs in the sandy Little Falls Dolostone, a part of the Upper Cambrian Beekmantown Group. The Little Falls contains abundant stromatolites, but few other visible fossils in most places. The quartz crystals were deposited by hydrothermal waters squeezed out of deeper rocks to the east during one of the Appalachian mountain building episodes (probably Taconian, but there is some controversy about this). Vugs can also contain well-formed crystals of dolomite and calcite. The quartz is associated with abundant anthraxolite (pyrobitumen) which colors parts of the rock black and can form good-size lumps. These represent the remains of hydrocarbons, probably once crude oil, that moved along with the flowing water. Minute traces of native platinum have been found in the anthraxolite (Parnell, 1988, American Mineralogist, v. 73, p. 1170-1171).


Map of the area

Map, highlighting Exit 30 on I-90 and the mine, campground, and museum location. See their web site for fees, hours, detailed directions, and camping. Basically, from the Herkimer Exit 30 on I-90, head north on Rt. 28 until you get there.

Students breaking rocks

How to find the diamonds? Step 1: Find a rock that speaks to you: "I have diamonds in me".

Students breaking more rocks

Step 2: Hit it. Most of the rocks are silent, or are lying to you. Sometimes you get lucky.

Student showing off tools

Tools of the trade: hammers of various sizes, goggles, patience, and a big smile.

Dismay: no diamonds!

This rock lied to me!

Frisbee after lunch

Playing frisbee after lunch, with the frisbee plates that came with the sandwich shop lunch.

Back to the mine pit

Back to the rock pile.

Checking for diamonds

After breaking a rock, look at the pieces for signs of diamonds.

Looking at the scenery

Smashing away all day at gray rocks can be tiring. Look at the scenary once in awhile. Outside of the gray quarry it is quite pretty.

Use big hammers for big rocks

All smiles when diamonds are found! Keep smashing, there might be more in there.

Group photo in the rock shop

This is what you look like after a day of smashing rocks. All smiles! This is inside the enormous gift shop, which has lots of rocks, minerals, Herkimer diamonds, and jewlery made from Herkimer diamonds. There is also a nice little museum upstairs, don't forget to take a look.

Photos (except map from Google) are ©Kurt Hollocher, 2010.