Comparison · Minerals
Gibbsite vs Howlite
Gibbsite and Howlite are easy to confuse because both are minerals. Both sit near Mohs 2.5–3.5, so a scratch test alone will not separate them. Lean on luster, streak and heft instead. Below is a side-by-side comparison of their properties and the quick tests that separate them.
Key differences between Gibbsite and Howlite
- Both sit near Mohs 2.5–3.5, so a scratch test alone will not separate them. Lean on luster, streak and heft instead.
- Hold a thin edge to the light: Gibbsite is Transparent to translucent, Howlite is Opaque.
- They overlap in white and gray, but Gibbsite also comes in green and red.
Gibbsite vs Howlite properties
| Property | Gibbsite | Howlite |
|---|---|---|
| Type | Minerals | Minerals |
| Mohs hardness | 2.5–3.5 | 3–3.5 |
| Luster | Vitreous, pearly on cleavage, dull when earthy | Subvitreous to dull |
| Streak | White | White |
| Transparency | Transparent to translucent | Opaque |
| Specific gravity | 2.3–2.4 | 2.45–2.6 |
| Crystal system | Monoclinic | Monoclinic |
| Common colors | White, Gray, Greenish, Reddish | White with gray veining |
| Rarity | common | common |
| Typical specimen value | $2–$150+ | $2–$150+ |
Which is more valuable?
Typical specimens of Gibbsite and Howlite trade in a similar range, around $20.
About Gibbsite
Gibbsite is aluminum hydroxide, Al(OH)3, a soft, typically white to gray mineral that forms as a weathering product in tropical and subtropical soils and serves as the principal ore mineral of aluminum within bauxite deposits. It commonly occurs as fine-grained, earthy masses or crusts rather than well-formed crystals, though occasional tabular pseudohexagonal crystals do develop in cavities. It is named after American mineral collector George Gibbs, whose collection helped found early American mineralogy.
About Howlite
Howlite is a calcium borosilicate hydroxide, Ca2B5SiO9(OH)5, typically found as white to gray nodular masses veined with dark, web-like markings that resemble turquoise. It crystallizes in the monoclinic system but rarely as distinct crystals, forming instead as compact, chalky nodules in borate-rich evaporite deposits. It was first described in 1868 by Canadian geologist Henry How, for whom it is named.
Gibbsite vs Howlite FAQ
Is Gibbsite the same as Howlite?
No. Both are minerals, but they are distinct species with different hardness, streak or luster. Both sit near Mohs 2.5–3.5, so a scratch test alone will not separate them. Lean on luster, streak and heft instead.
How can you tell Gibbsite from Howlite?
Both sit near Mohs 2.5–3.5, so a scratch test alone will not separate them. Lean on luster, streak and heft instead. Hold a thin edge to the light: Gibbsite is Transparent to translucent, Howlite is Opaque. They overlap in white and gray, but Gibbsite also comes in green and red.
Which is harder, Gibbsite or Howlite?
They are about equally hard, both near Mohs 2.5–3.5.
Which is more valuable, Gibbsite or Howlite?
Typical specimens of Gibbsite and Howlite trade in a similar range, around $20.
