Cuprite is a copper
oxide and a
major ore of copper. It is reddish in colour and transparent to
transculent. It forms mostly cubic crystals, but can also be
granular, compact, massive or earthy in habit. It is formed as a
secondary mineral when native copper is oxidised. It can be found in
oxidised copper deposits with native copper, azurite, malachite and
Zincite by Tjflex2 via Flickr.com
Zincite is a zinc
mineral and a less important zinc ore (the most important is
sphalerite). It is most often granular or massive, but rarely forms
pyramidal crystals. It is usually reddish to orangeish in colour, and
transparent to transculent. It is found in contact
rocks and in zinc ore deposits.
Magnetite is an iron
an important iron ore. As its name suggests, its most obvious property
is magnetism - it is the most magnetic mineral (after iron). It often
forms octahedral crystals but can also be granular or massive. It is a
very widespread mineral and occurs in many different environments. It
forms in igneous rocks and veins.
Hematite is also an iron oxide
and due to its high iron content (70%) it is the most important iron ore.
It can form crystals similar to magnetite, or be granular or massive.
It may look like magnetite, but it is not magnetic and its streak is
red while the streak of magnetite is black. Variations include
specular, massive, and iridescent hematite as well as kidney ore.
Chromate. By Jake Slagle via Flickr.com
Chromite is an iron
oxide mineral and the only important ore of chromium. It can form
crystals but is most often massive, nodular or granular. It is black,
dark grey or dark brown. It is often found in mafic and ultramafic
igneous rocks, as well as placer deposits. Chromite is weakly magnetic.
Cassiterite by Taifighta via Flickr.com
Cassiterite is a tin
the most important tin ore. It is most often dark in colour such as
black or brown, but may also be yellowish or colourless. It may form
crystals or be massive, reniform, botroydal or granular. It forms in
high temperature hydrothermal veins, where it can be found in granitic
rocks associated to tungsten minerals, quartz and chalcopyrite.
Rutile by cobalt123 via Flickr.com
Rutile is a titanium
is usually reddish brown, but can also be red, yellowish, or almost
black. Its crystals are most often prismatic, but can also be acicular
or slender. It is often found in granitic rocks and other igneous
rocks, as well
as metamorphics such as schists
can also be found in other minerals, such as rutilated quartz.
Ilmenite by Jake Slagle via Flickr.com
Ilmenite is another titanium
oxide mineral which is a major titanium ore. It forms crystals but can
also be granular, massive, lamellar or compact. It is dark brown or
black and can look like magnetite and hematite, but unlike
magnetite it is not magnetic, and unlike hematite it has a black
streak. It commonly forms in igneous rocks, pegmatites and hydrothermal
Corundum is an aluminium
oxide that forms some of the best known gemstones in the world - ruby
and sapphire. Apart from forming rhombohedral, tabular, or prismatic
crystals, it can also be granular or massive. It is the second hardest
mineral after diamond. It forms in igneous rocks that are poor in
silica and in metamorphics that are rich in aluminium.
Chrysoberyl by Gary Parent via Flickr.com
Chrysoberyl is a berylliumaluminium
oxide and a precious gemstone. Its gemstone variety -
is one of the hardest, rarest and most expensive gems in the world.
Chrysoberyl can form prismatic or tabular crystals, or be massive or
granular. It can be green or greenish
or brownish yellow. It
forms in many igenous and metamorphic
rocks but can also be found in placer deposits due to its
Spinel by Orbital Joe via Flickr.com
Spinel is a magnesiumaluminium
oxide mineral and some varieties of it are gemstones. It forms
octahedral crystals and can also be compact, granular or massive. It is
most often red but can also be blue, green, or black. It often forms in
aluminium rich metamorphic rocks and mafic igneous rocks but can also
be found in contact metamorphosed limestones.