Ruggles Mine

Useful Information

Location: Ruggles Mine Rd, Grafton, NH. NH Route 4 to Grafton, turn at church on town green, follow Ruggles Mine sign.
Open: 12-MAY to 14-JUN Sat, Sun 9-17.
15-JUN to 14-OCT daily 9-17.
15-OCT to 09- [2007]
Fee: Adults USD 20, Children (4-11) USD 10, Children (0-3) free.
Classification: Mica mine
Light: electric.
Guided tours:  
Address: Ruggles Mine, Tel: +1-603-523-4275.
As far as we know this information was accurate when it was published (see years in brackets), but may have changed since then.
Please check rates and details directly with the companies in question if you need more recent info.


1803 Mica first discovered in Grafton by Sam Ruggles.
1840 270kg to 320kg of mica mined annually.
1869 11 tons mined.
1874 owned and operated by J.W. Kelton.
JAN-1877 1630kg mica shipped in one month.
1932 purchased by the Bon Ami Company who mined feldspar for their non-abrasive scouring powder and glass cleaner.
1959 .
1963 mine closed.
1963 opened to the public.


The Littleton Formation which was formed during the Devonian, approximately 300Ma ago, is primarily mica schist, surrounding the Ruggles pegmatite. The Ruggles pegmatite is pretty huge, 500m long, 100m wide, and 75m deep.

In early Devonian the area was marine and sediments were deposited forming sandstone, siltstone, and shale. At the end of the Devonian the orogeny started, the rocks were folded, submerged, uplifted and metamorphized. The east-western compression created folds running north to south. Volcanism caused by the tectonic forces produced igneous rocks. The presence of volatiles during the crystallization permitted large crystals to grow.

The most impressive giant crystals here were books of mica, as large as 1.50m in diameter.


Located on Isinglass Mountain near Grafton, the Ruggles Mine is not really a mine, it is more like a quarry with numerous underground passages. This is not a show mine, there are no tours and no guides. The quarry is a fossicking site, where visitors can collect their own gemstones. Typical minerals found here are mica, feldspar, beryl, and uranium. The walls of white quartz and feldspar contain over 150 different minerals.

The first thing discovered here was mica, a thin, translucent silicate which is of great value. Not the value of gemstones, but pretty useful for various things. It was used to cover religious objects during the Middle Ages, as it was much more transparent than glass. Mica is heat resistant and transparent, so it was used for the windows in woodstoves and whale-oil lamps. Mica was also resistant against salt water, so it was used in ships windows. Until today it is used to insulate electricity. As it does not conduct heat or electricity, Early electrical toasters had mica in them.

Mica was first mined by the discoverer Sam Ruggles. He did not tell anyone about his find, mined secretly with his family, packed the mica into wagons along with farm product sand and sipped it secretly to Portsmouth. There it was shipped to England, where it was be sold without anyone at New Hampshire knowing. It is not clear why he was so paranoid, but one possible explanation is the ownership of the land. In the early 1800s land was claimed, not purchased, so he could claim a certain amount each year. Probably he wanted to keep the mine secret until he had claimed the entire mountain.