Identification guide · Minerals
How to Identify Grossular
Grossular's color varies dramatically from colorless and pale green to vivid tsavorite green, honey-yellow, cinnamon-orange hessonite, and reddish-brown, all sharing a vitreous luster and white streak. It has a hardness of 6.5 to 7.5, no true cleavage, and typically forms rounded dodecahedral or trapezohedral crystals in marble or skarn, sometimes as massive material resembling jade when compact and fine-grained. Grossular can be confused with other garnet species like andradite or spessartine, and its massive green form is sometimes mistaken for jade, but its crystal habit, hardness, and skarn or marble host rock help confirm the identification.
Grossular identification checklist
| Color | Colorless, Green, Yellow, Orange (hessonite), Brown, Pink | Look at a clean, dry surface in daylight. Color zoning, banding or spots are as diagnostic as the hue. |
|---|---|---|
| Luster | Vitreous to resinous | 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 | 6.5–7.5 | 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 | 3.4–3.8 | Heavier than it looks (specific gravity about 3.5999999999999996). |
| Crystal system | Cubic |
Extra tests for Grossular
Glass check. Grossular 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.
Grossular look-alikes and how to tell them apart
Both sit near Mohs 6.5–7.5, so a scratch test alone will not separate them. Lean on luster, streak and heft instead. Grossular vs Andradite →
Both sit near Mohs 6.5–7.5, so a scratch test alone will not separate them. Lean on luster, streak and heft instead. Grossular vs Hessonite →
Both sit near Mohs 6.5–7.5, so a scratch test alone will not separate them. Lean on luster, streak and heft instead. Grossular vs Garnet →
Both sit near Mohs 6.5–7.5, so a scratch test alone will not separate them. Lean on luster, streak and heft instead.
Grossular identification FAQ
How can you tell if a rock is Grossular?
Check the color (colorless, green, yellow, and orange (hessonite)), the vitreous to resinous luster, a Mohs hardness of 6.5–7.5 and a white streak. Photographing it with the StoneSnap app gives a match in seconds.
What is the hardness of Grossular?
Grossular has a Mohs hardness of 6.5–7.5. It scratches glass and a steel knife and cannot be scratched by a steel file.
What is the difference between Grossular and Andradite?
Grossular (Mohs 6.5–7.5, vitreous to resinous luster) and Andradite (Mohs 6.5–7, vitreous to resinous/adamantine luster) look alike, but hardness, streak and heft usually separate them. See the full Grossular vs Andradite comparison for a side-by-side table.
Is Grossular worth anything?
Entry-level Grossular 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 Grossular?
Grossular is most often colorless, green, yellow, and orange (hessonite). Color varies with impurities and locality, so confirm with hardness and luster rather than color alone.
