Identification guide · Minerals
How to Identify Chalcedony
Chalcedony shows a waxy to dull luster, is translucent to nearly opaque, and ranges through white, gray, blue, brown, and countless dyed colors, with a white streak. Hardness is 6.5 to 7, matching coarser quartz, and it breaks with a smooth conchoidal fracture rather than showing any cleavage. Banded, botryoidal, or nodular habits are typical. Chalcedony is often confused with jasper, which is simply an opaque, more heavily included variety of the same cryptocrystalline quartz family.
Chalcedony identification checklist
| Color | Blue-gray, White, Brown | Look at a clean, dry surface in daylight. Color zoning, banding or spots are as diagnostic as the hue. |
|---|---|---|
| Luster | Waxy to vitreous | Fresh surfaces shine like glass; a dull surface usually means weathering, so chip or wet a corner. |
| Transparency | Translucent | Hold a thin edge up to a bright light and note whether light passes through. |
| Mohs hardness | 6.5–7 | It scratches glass and a steel knife and cannot be scratched by a steel file. |
| Streak | White | Drag a corner across unglazed porcelain (the back of a bathroom tile) and check the powder color. |
| Cleavage | None | |
| Fracture | Conchoidal | Broken surfaces show smooth, curved, shell-like scoops. |
| Specific gravity | 2.6–2.64 | Ordinary rock-like heft (specific gravity about 2.62), similar to quartz. |
| Crystal system | Trigonal (cryptocrystalline) |
Extra tests for Chalcedony
Glass check. Chalcedony shares a glassy luster and conchoidal fracture with man-made glass. Glass sits near Mohs 5.5 and often contains round gas bubbles, so a hardness test and a hand lens separate them.
Chalcedony look-alikes and how to tell them apart
Both sit near Mohs 6.5–7, so a scratch test alone will not separate them. Lean on luster, streak and heft instead. Chalcedony vs Onyx →
Both sit near Mohs 6.5–7, so a scratch test alone will not separate them. Lean on luster, streak and heft instead. Chalcedony vs Agate →
Both sit near Mohs 6.5–7, so a scratch test alone will not separate them. Lean on luster, streak and heft instead. Chalcedony vs Blue Lace Agate →
Both sit near Mohs 6.5–7, so a scratch test alone will not separate them. Lean on luster, streak and heft instead. Chalcedony vs Dendritic Agate →
Chalcedony identification FAQ
How can you tell if a rock is Chalcedony?
Check the color (blue-gray, white, and brown), the waxy to vitreous luster, a Mohs hardness of 6.5–7 and a white streak. Photographing it with the StoneSnap app gives a match in seconds.
What is the hardness of Chalcedony?
Chalcedony has a Mohs hardness of 6.5–7. It scratches glass and a steel knife and cannot be scratched by a steel file.
What is the difference between Chalcedony and Onyx?
Chalcedony (Mohs 6.5–7, waxy to vitreous luster) and Onyx (Mohs 6.5–7, waxy to vitreous luster) look alike, but hardness, streak and heft usually separate them. See the full Chalcedony vs Onyx comparison for a side-by-side table.
Is Chalcedony worth anything?
Entry-level Chalcedony specimens sell for around $2, typical collector pieces about $20, and premium examples $150 or more depending on size, quality and locality.
What color is Chalcedony?
Chalcedony is most often blue-gray, white, and brown. Color varies with impurities and locality, so confirm with hardness and luster rather than color alone.
