By Adam Kelliher
The short answer: most rocks people find are worth very little in money, because common material is common. What lifts a price is rarity, quality (colour, clarity, crystal shape and damage), size, where it came from, and whether anyone actually wants to buy that material right now.
"How much is my rock worth?" is one of the most common questions people type into a search bar about our shop. I can't give you a number for a rock I can't see, and nobody honest can from a photo. What I can do is show you how a price gets set, so you can work out roughly where yours lands.
1. What it is
Start with the material. Quartz, jasper, basalt and granite are everywhere, so a plain piece sells for very little. Rarer minerals start higher. A quick way to see how common something is: Mindat's locality lists. A mineral with thousands of known localities is not going to be scarce.[1]
2. Quality
For cut gems, the trade works from the familiar 4Cs: colour, clarity, cut and carat weight. GIA describes coloured-stone quality with the same four factors.[2] Specimens follow similar logic. Sharp, undamaged crystals in a classic habit, good colour and a nice contrast with the matrix all add value. Chips, dings and repairs take it away. (For what habit means, see our crystal habits post.)
3. Size, and how it's sold
Rough rock for cutting and tumbling is usually sold by weight. Specimens and cut stones are priced piece by piece. A rule of thumb from the shop counter: a specimen's price doesn't rise in a straight line with size. A small, perfect crystal can be worth more than a big, broken one.
4. Where it came from
Locality matters to collectors. A specimen with a documented mine or site usually sells for more than the same mineral with no label. Some localities are famous for one mineral, and pieces from there carry a premium. Keep any labels and notes that came with your rock.[1]
5. Treatments and fakes
Dyed, heated, coated or stabilised material is worth less than the natural equivalent, and the seller should disclose it. GIA treats treatment disclosure as a basic part of describing a coloured stone.[2] Glass and plastic look-alikes are worth what the glass is worth.
6. Demand
Price is whatever a buyer will pay, and taste changes. A material that's in fashion can sell well above a scarcer one nobody's asking for. That's also why what you paid at retail isn't what you'll get back. We cover that in Why Your Crystal Collection Is Not Worth What You Paid for It.
So what do you do with your rock?
Work through the list honestly: what is it, how good is it, how big, where from, is it natural, and does anybody want it? If most answers are "common", enjoy it as a find. That's what most of mine are. To get a feel for real prices, browse comparable material in our rough rock and mineral specimens collections.
Hardness is one of the first clues to what your rock is, and what it might be worth. A Mohs hardness scale education set makes the test easy, and our post on the Mohs scale and true hardness explains the numbers.
See what's new: browse our newest arrivals for the latest pieces added to the shop.
Sources
- Mindat.org (Hudson Institute of Mineralogy): mineral and locality database.
- GIA (Gemological Institute of America): Colored Stones, the 4Cs and treatment disclosure.