Guide

Where to Find Mica in New Hampshire: USGS Records by County

Mica peels into thin, flexible, shiny sheets. In New Hampshire it comes mostly from pegmatite, the coarse granite where big crystals grew, and many old NH mines were worked for it.

What the USGS records show

After leaving out sand, gravel, crushed stone, clay and unnamed sites, 241 New Hampshire records mention mica, muscovite or biotite. Of those, 6 name the mineral in the record's mineral fields and 235 list mica only as a commodity, the thing the site was worked for. A commodity entry does not guarantee you will find specimens.

By record status: 121 prospect, 62 occurrence, 51 past producer, 5 producer. Status is as of the record, and USGS stopped systematic updates to this database around 2011.

Counties with the most mica records

1. Grafton County: 117 sites
2. Rockingham County: 74 sites
3. Cheshire County: 21 sites
4. Sullivan County: 11 sites
5. Merrimack County: 8 sites
6. Strafford County: 4 sites

See every record on mica sites in New Hampshire.

Where you can actually collect it

Almost all of these records are on private land with access unknown. One with verified public access is Ruggles Mine in Grafton, a former mica and feldspar mine that the operator runs as a fee dig ($30 per person, kids under 10 free, up to a 5-gallon bucket per admission; the operator says it reopens in spring 2027). The Forest Service lists muscovite among the minerals at the Deer Hill permit site.

How to recognize it

Mica has one perfect cleavage, so it splits into very thin sheets. Muscovite is light colored; biotite is dark. Hardness is about 2 to 3 on the Mohs scale, so a fingernail (2.5) may scratch it.

Sources: USGS MRDS (counts computed by RockWoof); Mineralogical Society of America, Mineral ID Key; Ruggles Mine; Mohs hardness from Mindat.

Rules checked against the linked sources on Oct 31, 2026. This is general information, not legal advice.