The Mineral & Gemstone Chrysocolla
Composition: Hydrated copper silicate
Crystal System: Orthorhombic or Monoclinic
Hardness: 2 to 4
Specific gravity: 2.0 - 2.3
Luster: vitreous to waxy.
Streak: white to blue-green
Transparency: translucent to opaque
Associated Minerals: azurite,
malachite, cuprite, other secondary copper minerals, limonite, quartz
Hydrated copper silicate CuSiO3 - nH2O
(45.2% CuO, 34.3% Si03, 20.5%
Sky-blue to greenish blue and green, often streaked with
black. Some specimens may have shades of all of these colors. Chrysocolla
is mostly in massive forms that can be crusts, stalactites and botryoidal.
It is also found as inclusions in other minerals.
Most likely to be confused with turquoise, which
is much harder #6, and cannot be scratched by a knife. Also confused with chrysocolla - impregnated chalcedony, or quartz, which is also hard.
In the oxidized zone of copper deposits, mainly in arid
Microcrystalline, usually in solid vein-filling or botryoidal masses,
often opal-like in appearance. Slender needles have been described as
crystals but were only found at one locality (Mackay, Idaho).
Tongue usually clings to specimen. Blackens and gives water in the closed
tube. Practically infusible, but decomposed by hydrochloric acid with
a separation of silica.
Chrysocolla occurs very widely in the American
Southwest in copper deposits. Blue chrysocolla impregnated quartz, covered
by small crystals of white quartz, from the Globe Mine, Gila County, Arizona,
are frequent in collections. Fine massive specimens were found, in the
early stages, in most of the western United States copper mines. Also
found today in Africa and Chile. Russia and England (Cornwall and Cum-
berland) once produced good specimens.
Chrysocolla was used in the West like turquoise for
jewelry, but pure chrysocolla free of quartz is rather fragile and likely
to crack. However, chrysocolla is often "agatized" in chalcedony quartz.
The quartz provides the stone with its polish and durability. A famous
form of this came from Mexico many years ago. It was called Parrot Wing.
Another nice form is Drusy Chrysocolla. It is composed of agatized chrysocolla
with a crust of small sparkling quartz crystals in small cavities. Polished
specimens that show the vivid blue-green of chrysocolla and sparkling
drusy quartz on top, can be quite pretty. .It is also an ore of copper
when it is mixed in with other secondary copper minerals. Chrysocolla's most popular use
is as rare mineral specimens.
FACTS & HISTORY:
Named from the Greek chrysos - "gold" and kolla - "glue"
in allusion to the name of the material used to solder gold.