Unopened Geodes: How to Pick One That Is Hollow

Most geodes are not hollow. The Kentucky Geological Survey states it plainly: most geodes are completely filled with minerals, and only the hollow ones have the crystal-lined cavity everyone is hoping for. Rock & Gem magazine puts a number on it for one well-documented deposit — at Las Choyas in Chihuahua, Mexico, about 80% of the mined geodes turn out to be solid.

That is the frame for every unopened geode purchase. You are buying a lottery ticket with better-than-lottery odds, and there is no test that makes it a certainty short of cutting.

Solid ones are not a total loss. The same report notes solid Las Choyas cores are used in the lapidary trade for cabochons and for bookends and similar objects, because solid agate cuts and polishes beautifully.

• Heft it against its size. This is the one test every geological survey mentions. The Iowa Geological Survey's rule is that for the same size, a hollow geode lined with crystals is noticeably lighter than a solid nodule. Pick up three geodes of similar diameter and keep the lightest.
• Read the rind. Hollow geodes tend to have a thick, bumpy chalcedony crust. The Kentucky Geological Survey describes that outer shell of quartz — usually chalcedony — as the defining feature of a hollow geode. A smooth, dense, heavy stone with no knobbly crust is more likely a plain nodule.
• Find a natural chip. Field-collected geodes almost always have one small break somewhere. Wet it with a thumb and look for concentric banding, and for any glint of crystal.
• Shake it. Some hollow geodes rattle because a crystal or a piece of rind came loose inside. A rattle is good news; silence proves nothing.

Unopened geodes are listed under half a dozen names — uncut, unbroken, whole, closed, crackable, break-your-own — and they mean the same thing. What differs is how the seller sorted them.

• Mine-run means unsorted, straight from the diggings. Cheapest by weight, worst odds.
• Graded or hand-picked means someone weighed or candled them and pulled the light ones. Better odds, higher price.
• Guaranteed hollow should mean the seller checked each one, often by weight or by a small saw cut. Ask how they checked. A seller who cannot answer is guessing.

Buying a small graded lot usually beats buying a big mine-run lot, because a single good cavity is worth more than a bucket of solid cores.

Two of the best-known American localities are open in very different ways.

Dugway Geode Beds, Utah. The beds sit on Bureau of Land Management public land in Utah's West Desert, reached from Interstate 80 exit 99 and then roughly 83 miles along the Pony Express Trail to an unimproved road. Geodes there are typically two to four inches, appearing as hard, dark grey spheres, most often filled with clear, purple or pink quartz. The BLM's own safety rule is firm: tunnelling is unsafe and not permitted, because the soft digging material can collapse. Bring water, a spare tyre and tell someone your route.

Southeastern Iowa. The Iowa Geological Survey is equally direct: most geode-collecting localities there are on private land and permission must be secured before entering or removing rocks, and geode collecting is not permitted in state parks. That includes Geode State Park, which takes its name from the geodes rather than offering them for collecting.

Decide what you want from the piece first, because you only get one chance. A saw gives two flat, polishable faces; a chain pipe cutter usually gives two rough halves; a hammer gives fragments. Rock & Gem's guidance is that a hammer alone will more likely shatter a geode than halve it.

Whatever method you pick, eye protection is not optional — a chip off the rock or the hammer can injure anyone standing nearby. For children, put the geode inside an old sock before striking it so the pieces stay contained. Full step-by-step instructions are on our page about cracking a geode.

A crackable geode is simply an unopened geode sold for you to break yourself. The listings that rank for the term show what you get at each price, all checked on 25 September 2026:

• Moroccan quartz geodes, 3 to 4 inches: US$5 each at FossilEra, with bulk discounts. Amazon sells boxed sets of Moroccan geodes of about 2 inches in twenties.
• Wack n' Crack amethyst tube, The Gem Shop: US$11.99 for three to five geodes. The seller says these have small openings with individual crystals, sometimes double-terminated, rather than a big hollow, and that cracking can leave loose crystals. It recommends cracking rather than sawing, with adult supervision.
• Las Choyas geodes from Mexico, 3.5 to 3.75 inches: US$55 each at FossilEra. Rock & Gem reports about 80% of mined Las Choyas geodes are solid, so the price reflects the chance of a good cavity rather than a promise of one.
• Keokuk geodes, already opened: polished pairs of 2.3 to 2.6 inches at US$22 to US$27 a pair at FossilEra, if you would rather see the inside before paying.

Cheap kits are the right choice for children and first attempts. Sorted single geodes are the better buy if you want a display piece.

Breaking one is easy; breaking it into two clean halves is not. The shell is quartz, which is 7 on the Mohs scale used by the U.S. Geological Survey, so it resists a hammer until it suddenly shatters. The Bureau of Land Management describes the Dugway geodes of Utah as hard, dark grey spheres, and Rock & Gem warns that a hammer alone will more likely shatter a geode than halve it.

What makes it manageable:

• Small geodes are easiest. The 2 to 4 inch size sold in kits breaks with one firm blow inside a sock.
• Score first. Tapping a line all the way round with a flat chisel, then striking, gives far better halves than one heavy blow.
• Use even pressure for good pieces. A chain pipe cutter squeezes all the way round and is the household tool most likely to give two equal halves.
• Always wear eye protection, and keep bystanders back.

Step-by-step methods are on our cracking a geode page.

Beyond Dugway and the Iowa private land covered above, the sources we opened add these:

• Kentucky. The Kentucky Geological Survey says the Fort Payne and Warsaw-Salem formations, of Mississippian age, contain numerous geodes, and that they also turn up in creeks draining those formations, along the Green River in south-central Kentucky, where some reach 2 feet across, and on ancient terraces of the Kentucky River.
• Geode State Park, Iowa. Look but do not take. The Iowa Department of Natural Resources says geodes are on display in the park office and it is prohibited to remove geodes from the park.
• The American Southwest. The Geology In site lists California localities such as Calico Ghost Town, Hollister Hills State Park, Death Valley and Owens Valley; Arizona sites around Cave Creek, Superior and Bisbee; and Texas sites around Marfa, Balmorhea and Big Bend. Several are parks where collecting may be banned, so treat the list as a starting point and check each site's rules before digging.

On any public or private land, the rule is the same: confirm who manages it and whether collecting is allowed before you take a single rock.

The sections added on 25 September 2026 were researched and drafted with AI assistance and checked line by line against the sources listed on this page. Prices are dealer asking prices seen on that date, not appraisals.