Identification guide · Minerals
How to Identify Andradite
Andradite typically shows a resinous to adamantine, sometimes vitreous luster in colors from yellow-green through brown to black, paired with a white streak despite its dark body color. It has no cleavage, breaking instead with a conchoidal to uneven fracture, and a hardness near 6.5 to 7 resists a steel knife. Crystals commonly form as dodecahedrons or trapezohedrons. It is easily confused with other garnet species such as grossular and, in dark massive form, with tourmaline or epidote.
Andradite identification checklist
| Color | Yellow-green (demantoid), Brown, Black (melanite), Yellow | Look at a clean, dry surface in daylight. Color zoning, banding or spots are as diagnostic as the hue. |
|---|---|---|
| Luster | Vitreous to resinous/adamantine | Fresh surfaces shine like glass; a dull surface usually means weathering, so chip or wet a corner. |
| Transparency | Transparent to 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 to uneven | Broken surfaces show smooth, curved, shell-like scoops. |
| Specific gravity | 3.8–3.9 | Heavier than it looks (specific gravity about 3.8499999999999996). |
| Crystal system | Cubic |
Extra tests for Andradite
Glass check. Andradite 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.
Andradite 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. Andradite vs Grossular →
Both sit near Mohs 6.5–7, so a scratch test alone will not separate them. Lean on luster, streak and heft instead. Andradite vs Almandine →
Both sit near Mohs 6.5–7, so a scratch test alone will not separate them. Lean on luster, streak and heft instead. Andradite vs Hessonite →
Both sit near Mohs 6.5–7, so a scratch test alone will not separate them. Lean on luster, streak and heft instead.
Andradite identification FAQ
How can you tell if a rock is Andradite?
Check the color (yellow-green (demantoid), brown, black (melanite), and yellow), the vitreous to resinous/adamantine 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 Andradite?
Andradite 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 Andradite and Grossular?
Andradite (Mohs 6.5–7, vitreous to resinous/adamantine luster) and Grossular (Mohs 6.5–7.5, vitreous to resinous luster) look alike, but hardness, streak and heft usually separate them. See the full Andradite vs Grossular comparison for a side-by-side table.
Is Andradite worth anything?
Entry-level Andradite 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 Andradite?
Andradite is most often yellow-green (demantoid), brown, black (melanite), and yellow. Color varies with impurities and locality, so confirm with hardness and luster rather than color alone.
