Pyrite,
aka
fool's gold, is a common mineral in all types
of rocks.
It is metallic, opaque and while most known for its cubic crystals, can
also have pyritohedral or octahedral crystals, or be granular, massive,
reniform or potryoidal in habit. It is pale silvery-yellow when fresh
but gets darker as it tarnishes.
Chalcopyrite
is deeper yellow than pyrite, but it is also metallic, opaque, and can
occur in massive, botryoidal, reniform or compact habits. It is often
found in hydrothermal sulphide deposits, where it has formed in
hydrothermal veins. It is an important copper ore.
Galena
Galena by
Mike Beauregard via Flickr.com
Galena is
a
sulphide mineral,
more exactly a lead sulphide. It is a common ore mineral and often
found in lead-zinc-copper hydrothermal depositis. It is lead-grey in
colour and often forms crystals but can also be found as massive
habits. It is often associated with other minerals such as pyrite,
chalcopyrite, sphalerite, calcite, quartz and fluorite.
Sphalerite
Sphalirite, Ian
Geoffrey Stimpson via Flickr.com
Sphalerite
is zinc sulphide. It
is not common on its own, but more often in alloy with iron. It is
greenish without iron, black with little iron, and reddish with much
iron. It has coarse crystals and is often massive, and it can form
stalactitic or botryoidal aggregates. It is mainly found in
hydrothermal lead-zinc depositis and it is a main zinc ore.
Azurite is
a
deep azure blue copper hydroxide. It can be earthy, nodular or massive,
or it can form prismatic crystals. It is found in the oxidised zones of
copper deposits, which have formed in limestone and other carbonate
rocks. Like other carbonates, it reacts to HCl.
Malachite
is
a pale to dark green common secondary copper mineral. It can be
botryoidal or stalactitic, or form prismatic, circular or twinned
crystals. It can be transculent to opaque, and it is formed in the
oxidised parts of copper deposits, often together with azurite.
Malachite has been used extensively in jewelry, and even to decorate
palaces.
Hematite
is
an iron oxide which can be very various in appearance. Specular
hematite for example comes in a hexagonal, platy, shiny,
silver-coloured crystal. Massive hematite is reddish brown and has a
massive, earthy habit. Kidney ore is red and reniform. Hematite is
found in hydrothermal veins, contact metamorphic rocks, volcanic
fumeroles, and ironstones.
Calcite, a
common carbonate mineral, is either transculent or transpalent, and can
come in many colours such as colourless, white, red, grey, green,
brown, or black. It can be massive, fibrous, granular or stalactitic,
or form prismatic, rhombohedral or scalenohedral crystals.
It is the main mineral in limestones and marbles.
List of all
minerals - Beryl
Mineral beryl by
Orbital Joe via Flickr.com
Beryl is a
silicate mineral, which can either be massive and in other earthy
habits, or form beautiful crystals that, depending on their colour,
have a name amongst gemstones.
It can be red, white, colourless, green (emerald), blue (aquamarine), yellow (heliodor), and pink (morganite). It forms mostly in igneous
rocks related to
granites, but can also be found in schist.
Olivine
is
an iron and magnesium rich silicate mineral (like many other minerals,
it is actually a solid solution, i. e. a group of minerals which vary
in compositions between the iron-rich end member fayalite and the
magnesium rich end member fosterite. They are most often green, but can
also be brown, grey, white or yellow. It is found in mafic rocks.
Garnet is
also a group of minerals such as grossular, almandine, spessartine and
pyrope garnet. Spessartine is greenish, while the others are reddish in
colour. They all have cubic crystals (pyrope's are rounded cubics),
while grossular is transculent and the others are opaque.
Almadine is the one that occurs in garnet schist.
Corundum
is
an aluminium oxide mineral, which, just like beryl, forms crystals that
are known amongst gemstones, such as ruby
(red), padparadscha
(pink),
and white, blue, orange, violet, green and yellow sapphire. But it can
also be granular or massive, or mixed with magnetite (emery). Corundum is
found in pegmatites, syenites, and gneiss.
Zircon
also
forms crystals known as gemstones,
however they are all called zircons. They can be red, yellow, brown,
green, grey or colourless. Zircon can form irregular grains,
fibrous aggregates or prismatic crystals. It can be transparent or
opaque. Zircon can contain traces of uranium and be slightly
radioactive.
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