THE MINERAL ROSASITE
- Chemistry: (Cu, Zn)2CO3(OH)2 ,
Copper Zinc Carbonate Hydroxide
- Class: Carbonates
- Group: Rosasite
- Uses: very minor ore of zinc and copper and as a mineral
specimen
- Specimens
Rosasite forms in the oxidation zones of zinc-copper deposits.
It typically is found as crusts and botryoidal masses or nodules.
Crystals are fibrous and found in tufted aggregates. The color
is an attractive bluish green. Rosasite is associated with red
limonite and other such colorful minerals as aurichalcite, smithsonite
and hemimorphite. Nodules of rosasite certainly add color to what
are termed "landscape" specimens.
Rosasite can be confused with Aurichalcite, (Zn, Cu)5 (CO 3 )2(OH)6 .
However rosasite is usually more massive but not lamellar. Rosasite
crystals are harder than aurichalcite; 4 versus 1 - 2 respectively.
PHYSICAL CHARACTERISTICS:
- Color is usually a bluish-green to green.
- Luster is silky to vitreous to dull for massive specimens.
- Transparency: Crystals are transparent to translucent.
- Crystal System is monoclinic; 2/m
- Crystal Habits include radiating tufts of fibrous crystals.
It typically is found as crusts and botryoidal masses or nodules.
- Hardness is 4
- Specific Gravity is approximately 4 (somewhat heavy
for non-metallic minerals)
- Cleavage is perfect in one direction but not usually
noticed because of fibrous crystal habit.
- Fracture is fibrous.
- Streak is pale shades of bluish green or green.
- Associated Minerals include limonite,
smithsonite,
hemimorphite,
malachite,
aurichalcite
and calcite.
- Other Characteristics: Effervesceses easily in cold
dilute hydrochloric acid.
- Notable Occurrences include Arizona, New Mexico and
Inyo Co., California, USA; Rosas Mine, Sardinia, Italy; Tsumeb,
Namibia and Mapimi, Durango, Mexico.
- Best Field Indicators are crystal habits, color, associations,
hardness and reaction to acid.