Ace of Diamonds Mine Closed: Where to Dig Instead

Ace of Diamonds Mine in Middleville, New York, is closed. The mine’s own website says the mine, campground and gift shop are closed until further notice and that digging and camping are not expected to be available for the whole 2026 season (Ace of Diamonds Mine & Campground, read 16 October 2026). If you want to dig Herkimer diamonds this autumn, the open option is the Herkimer Diamond Mines in the same village of Middleville, which lists daily hours until 31 October 2026 and charges $19 for adults on weekdays. Below you will find which mines are open, what a day costs, how to dig, and what the rock and the crystals really are.

Herkimer diamonds are not diamonds. They are doubly terminated quartz crystals, meaning they have a point at both ends, and they grow in small cavities called vugs inside a Late Cambrian rock called the Little Falls Dolostone (Geology.com, Hobart King). Every price and date on this page names its source and the day it was read.

Is Ace of Diamonds Mine open?

No. The home page of the Ace of Diamonds Mine & Campground carries a notice that the mine, the campground and the physical gift shop are closed until further notice. A second announcement on the same page says camping and mining are expected to be unavailable for the entire 2026 season, while the online shop keeps selling (Ace of Diamonds Mine & Campground, read 16 October 2026). The business describes itself as family owned and operated for over 50 years. It has not published a reopening date, so call or check the site before planning a trip for 2027.

Older travel pages still list the mine as open from April to October, which is why the closure surprises visitors. One directory entry recorded adult admission of US$14 and US$7 for children aged 4 to 7 in 2022, and gave the location as Middleville (ShowCaves, fee data from 2022). Those figures are history, not a current price list.

The same directory notes that the Ace of Diamonds Mine and the Herkimer Diamond Mine sit only about 500 metres (roughly 550 yards) apart. They work the same dolostone belt, so a closure at one gate does not mean the rock is different at the other.

Where to dig Herkimer diamonds instead

Geology.com names three commercial mines along New York State Routes 28 and 29 near Middleville where visitors pay a fee to prospect: the Ace of Diamonds Mine, the Herkimer Diamond Mines and the Crystal Grove Diamond Mine and Campground (Geology.com). Their status on 16 October 2026 is below.

Sources: Herkimer Diamond Mines, Crystal Grove and Ace of Diamonds, all read 16 October 2026. Hours and closures change with weather and ownership decisions, so check the mine’s site on the morning you drive.

How we chose what to list

We included only mines that charge the public to dig on the surface in the Middleville and Mohawk Valley belt and that appear in Geology.com’s list of commercial mines. For each one we used the operator’s own website for status, hours and prices, and we read those pages on the date shown. A mine that does not publish a current season is shown by its last public statement, not guessed.

Some of the same dolostone is also studied by researchers. A Rutgers University project plans to drill the full Little Falls Dolostone at the Treasure Mountain Diamond Mine in Little Falls, which would recover 400 to 500 feet of core (Rutgers Department of Earth and Planetary Sciences). That is a research site, not a dig we are rating.

Herkimer Diamond Mines admission and sluice bag prices

The operator lists a 2026 price for an all-day prospecting ticket that includes gem collection bags and use of a rock hammer. Adults and children aged 13 and over pay US$19; ages 5 to 12 pay US$16; children aged 4 and under are admitted at no charge. Fridays, Saturdays and Sundays add US$3 for the older group and US$2 for the younger group. Active military get a discount with ID (Herkimer Diamond Mines, 2026 season).

Chart

Herkimer Diamond Mines all-day ticket by age group

US$ per person, 2026 season

Hammer rental is included, but the mine keeps your ID or licence until the hammer is back. Admission tickets and closed-toe shoes are required in the mines, eye protection is strongly recommended, and tools over 12 pounds or any powered equipment are not allowed.

The sluice station is a separate activity. You buy a bag of material, rinse it over a screen and sort what is left. The mine states that every bag contains guaranteed finds, and that only the Herkimer Diamonds Dirt Bag contains Herkimer diamonds. Bags cost US$18 to US$30 and three bundled packages run from US$35 to US$85, as shown in the chart below.

What a day dig costs for a family

Admission is only part of the bill. Two adults and two children aged 5 to 12 on a weekend, with two Dirt Bags, come to about US$122 before travel (US$80 admission and US$42 for two bags, using the calculator defaults). Use the calculator to try your own party size, weekend surcharge and bags.

Chart

Sluice bags and packages at Herkimer Diamond Mines

US$ per item, 2026 season

Driving time from nearby cities

One rockhounding directory gives approximate drive times to the Herkimer area: Syracuse about 1 to 1.5 hours, Albany about 1.5 to 2 hours, New York City about 3.5 to 4.5 hours, and Boston or Philadelphia about 4 to 5 hours (Rockhounding Sites). From New York City or beyond, most visitors treat it as an overnight trip rather than a day trip.

How to dig Herkimer diamonds: the on-site process

Dolostone is a tough rock, and at the dig sites it is usually heavily silicified, which makes it harder still. Geology.com describes three ways visitors work it (Geology.com):

Infographic

A dig day in 5 steps

1. 1Check statusConfirm hours and closures on the mine’s own site that morning.
2. 2Sign in and gear upPay admission, show ID for the rental hammer, wear closed-toe shoes and eye protection.
3. 3Choose rockLook for dolostone with visible vugs, or search the rubble for loose crystals.
4. 4Split carefullyUse small controlled blows, chisels or wedges; stay clear of flying chips.
5. 5Sort and wrapWrap points in soft paper and keep cloudy crystals; finds are yours at the Herkimer Diamond Mines.

• Find and break. Pick up rocks that show vugs on the outside and split them with a heavy hammer. Most vugs turn out empty, so many broken rocks will hold nothing.
• Scavenger prospecting. Search rubble and the quarry floor for loose or exposed crystals. This is the safest method for children.
• Cavity prospecting. Open large cavities in the quarry walls and floor with sledge hammers and wedges. It takes tools, patience and time, and the article notes that power equipment is not permitted at the mines it lists.

The Herkimer Diamond Mines FAQ adds that pockets are local rich zones, typically 1 to 6 feet wide with a dome-like top. It reports crystals up to 8 inches long in the largest pockets and say the clearest stones are usually under 1 inch long (mine FAQ). That is the owner’s description, not a measured survey.

What to wear and bring

Wear closed-toe boots, long trousers and a long-sleeved shirt, because chips of dolostone fly when rock breaks and can cut bare legs. Add safety glasses or goggles and gloves. The mine suggests chisels, hand screens, small shovels, buckets and hammers up to 12 pounds if you bring your own. Take water and sun protection, as repeated hammering is tiring.

What you can find in the dolostone

A 1992 field guide from Utica College lists dolomite, calcite, quartz and a solid black hydrocarbon called anthraxolite as the most common minerals in the Little Falls Dolostone (Muskatt and Tollerton, NYSGA guidebook, 1992). Anthraxolite shows up as black specks or streaks inside clear crystals, and the mine points to enhydro crystals, which hold a water bubble, as an extremely lucky find. Other forms named by the mine include twins, clusters, smoky crystals, skeletal crystals and phantoms.

The mine says all pockets hold very small shining crystals and that clarity usually falls as crystals get bigger. Everything you find there is yours to keep, according to its FAQ.

Why Herkimer diamonds are quartz, not diamond

Herkimer diamonds are silicon dioxide (SiO2), the same chemistry as sand and ordinary quartz, with a Mohs hardness of 7 and a specific gravity of 2.6 to 2.7 (Geology.com). The Handbook of Mineralogy lists quartz at hardness 7 and names Middleville in Herkimer County as a locality (Handbook of Mineralogy, quartz). Some mine pages quote 7.5, but the mineralogy references put quartz at 7, one point below topaz and three below diamond, so a Herkimer will not scratch a real diamond.

Chart

Mohs hardness: Herkimer diamond quartz against other minerals

Mohs scale, 1 to 10

Their double points come from growing with little or no contact with the host rock. The host is the Little Falls Dolostone, deposited about 500 million years ago, and the crystals grew in cavities that are often lined with drusy quartz and coated with tarry hydrocarbon (Geology.com). The formation is about 200 feet thick at Middleville, according to the 1992 field guide.

How old are the crystals?

You will often read that the crystals are 500 million years old. That is the age of the rock, not necessarily of the quartz. The 1992 guide says the origin of the minerals is complex and unresolved, and describes the age of the quartz as presently accepted as Carboniferous, which is much younger than the Cambrian host rock. A Rutgers researcher writes that no one has a definite answer on how or when the crystals formed (Rutgers). The Ace of Diamonds site puts the cavities at roughly 400 million years.

▶ Explains remote sensing for mining in plain words, covering the instruments that measure ground from a distance. · 2:01

Collecting rules in New York

All land in New York is either government land or private property. Collecting minerals on private land needs the owner’s permission in advance, and that is the reason fee mines exist (Geology.com). On state land the New York State Department of Environmental Conservation says that removing plants, rocks, fossils or artifacts without a permit is illegal (NYS DEC, state land rules). Do not dig on roadsides, stream banks or farm fields without written permission.

Rules differ by state. For background on the mineral itself, read our overview of where quartz is found around the world. Never use mercury, and leave pits level and safe when you finish.

▶ A claymation on the 7 environmental impacts of mining and how land is affected. · 2:31

What the Middleville quarries look like from space

The Middleville quarries are small pits and spoil heaps in a farm and forest landscape. The Sentinel-2 image at the top of this page is a multi-year composite of this area, so it shows the landscape around the quarries rather than any single day’s workings. Satellite imagery cannot show where a vug is, because a cavity under a few feet of rock is invisible from orbit.

Farmonaut’s mining service takes a KML, KMZ or polygon of your area and screens it from satellite data for exploration targets, ahead of any resource estimate. For a general look at the minerals people search for from orbit, see our overview of diamond exploration from indicator grains to kimberlite pipes, which covers true diamonds.

▶ A quick look at Farmonaut Mining Pro, which turns a licence boundary into a geological and economic picture. · 4:56

For a closer look at a related question, see our guide: How to Dig for Diamonds in Arkansas: 6 Steps and Costs.

If this topic matters to you, read Blue Lace Agate Mine: Location, Status and Fire Agate next.

Frequently asked questions

Is Ace of Diamonds Mine open?

No. The mine, campground and gift shop are closed until further notice, and the owner says digging and camping are expected to be unavailable for the whole 2026 season (Ace of Diamonds Mine & Campground, read 16 October 2026).

Where can I dig Herkimer diamonds right now?

The open Middleville mine lists daily hours of 9 AM to 5 PM from 12 April to 31 October 2026. Crystal Grove is closed for 2026 and reopens on 16 April 2027.

How much does it cost to dig Herkimer diamonds?

In 2026 the ticket is US$19 for ages 13 and up and US$16 for ages 5 to 12, with a US$3 or US$2 weekend surcharge. Children aged 4 and under are admitted at no charge. Sluice bags cost US$18 to US$30.

Are Herkimer diamonds real diamonds?

No. They are quartz (silicon dioxide) with a Mohs hardness of 7, while diamond is 10 (Geology.com).

Can I keep what I find?

At the Middleville mine that is open, yes: everything you find is yours to keep, according to the mine’s FAQ.

What tools do I need?

A 2 to 3 pound crack hammer and a chisel are the most popular tools, per the mine. Rental hammers are included with admission, you need closed-toe shoes, and eye protection is strongly recommended. Tools over 12 pounds and powered equipment are not allowed.

How old are Herkimer diamonds?

The host rock formed about 500 million years ago. The quartz inside is accepted as Carboniferous in a 1992 field guide, which makes it younger, and researchers still say the exact timing is unresolved.

Can I dig on public land in New York?

Not without a permit. The DEC says removing rocks, fossils or artifacts from state land without a permit is illegal. On private land you need the owner’s permission.

How long does it take to drive from New York City?

About 3.5 to 4.5 hours, according to one rockhounding directory, so many visitors stay overnight.

Where exactly do Herkimer diamonds come from?

They come from vugs in the Little Falls Dolostone, a Late Cambrian rock that crops out around Middleville and Little Falls in Herkimer County (Geology.com; Muskatt and Tollerton, 1992).