2009,
March 25. Philippine Minerals
Litho Offset.
Amstar Company, Inc. Perf. 14.
Se-tenant Blocks
of 4 (10 Blocks per sheet) , Sheets of 40 (4 x 10); Souvenir Sheets
of 4
Se-tenant Blocks of Four
(25,000)
7p Quartz
7p Rhodochrosite
7p Malachite
7p Nickel
Souvenir Sheets of Four
(5,000)
7p Cinnabar
7p Native Gold
7p Native Copper
7p Magnetite
First Day Covers: Manila
Official FDCs: 2 different
designs; 400 each issued at
P72 a pair
PHILIPPINE MINERALS
7p Quartz -
Quartz belongs to the
rhombohedral
crystal system. The
ideal crystal
shape is a six-sided
prism
terminating with six-sided
pyramids
at each end. In nature quartz crystals are often
twinned,
distorted, or so inter-grown with adjacent crystals of quartz or
other minerals as to only show part of this shape, or to lack
obvious crystal faces altogether and appear massive. Well-formed
crystals typically form in a 'bed' that has unconstrained growth
into a void, but because the crystals must be attached at the other
end to a matrix, only one termination pyramid is present. A quartz
geode
is such a situation where the void is approximately spherical in
shape, lined with a bed of crystals pointing inward. (http://en.wikipedia.org/wiki/Quartz)
7p Rhodochrosite - Rhodochrosite (whose name means
rose-colored) is a very attractive mineral with an absolutely
one-of-a-kind, beautiful color. Although it can be an ore of
manganese, it is its ornamental and display specimen qualities that
make it a very popular mineral. The color of a single crystal can
just astound the observer with its vivid pink-rose color that seems
to be transmitted out of the crystal as if lit from within. (http://www.galleries.com/minerals/CARBONAT/RHODOCHR/rhodochr.htm)
7p Malachite - Malachite is a green mineral with a widely
variable habit. Typically it is found as crystalline aggregates or
crusts, often banded in appearance, like agates. It is also often
found as botryoidal clusters of radiating crystals, and as
mammillary aggregates as well. Single crystals and clusters of
distinguishable crystals are uncommon, but when found they are
typically acicular to prismatic. It is also frequently found as a
pseudo morph after
Azurite
crystals, which are generally more tabular in shape. (http://www.mindat.org/min-2550.htm)
7p
Nickel - The vast nickel laterites of Surigao in northeastern
Mindanao were first reported in 1912, although these were not
exploited until 1975. The first production of nickel in the
Philippines was from nickel sulphide, which was found during the
course of chromite mining at Acoje, Zambales. Up to 400 metric tons
of beneficiated nickel sulphide were produced from 1970 to 1976.
The nickel deposits at Nonoc, Surigao del Norte were mined from 1975
to 1982. The escalating cost of fuel soon posed problems because of
the energy intensive recovery process involved. During this period,
production of nickel (as metal) ranged from 9,600 to 25,000 metric
tons per annum. (http://www.mgb.gov.ph/asomm/min_resources.htm)
7p Cinnabar - Cinnabar is a colorful
mineral that adds a unique color to the mineral color palette. Its
cinnamon to scarlet red color can be very attractive. Well shaped
crystals are uncommon and the twinned crystals are considered
classics among collectors. The
twinning
in cinnabar is distinctive and forms a penetration twin that is
ridged with six ridges surrounding the point of a pyramid. It could
be thought of as two scalahedral crystals grown together with one
crystal going the opposite way of the other crystal. Cinnabar was
mined by the Roman Empire for its mercury content and it has been
the main ore of mercury throughout the centuries. Some mines used by
the Romans are still being mined today. Cinnabar shares the same
symmetry class with quartz but the two form different crystal
habits. (http://www.galleries.com/MINERALS/sulfides/cinnabar/cinnabar.htm)
7p Native Gold
- Lode and placer gold deposits occurring most
of the 73 provinces in the Philippines. The principal producing
districts are Baguio and Paracale in Luzon; and Masbate, Surigao and
Masara in Mindanao. Gold production in 2003 totaled 37,800 kg
compared to 35,800 kg in 2002.
7p Native
Copper - Mining of copper in the Philippines also has a long
history although until the second half of this century it was
inferior to gold in value. Crudely-smelted copper was traded with
the Chinese in the 14th Century. Late in the Spanish era copper
mines were opened at Carawisan (in Panay) in 1842 and at Mankayan
(northern Luzon) in 1864. In 1974, there were 18 copper mines in
operation, most of them of porphyry-type. Production peaked at
304,500 metric tons of copper in metal in 1980, but declined
markedly beginning 1982. For the past several years, annual
production has averaged around 200,000 metric tons. Constituting 35%
of the country’s mine production by value. As mentioned earlier,
gold and silver are important by-product of copper mining. (http://www.mgb.gov.ph/asomm/min_resources.htm)
7p Magnetite - Collected at the water depth of 1989 meters on
the Benham Rise of the western Philippine Sea, composed of
olive-brown hemi-pelagic calcareous oozes and intercalated with
volcanic ash layers in 1-15 cm thickness. Analysis of magnetic
mineralogy and granulometry reveals that the main magnetic carrier
of sediments is magnetite with grain sizes within the range of
pseudo-single domain. (http://www.earth.sinica.edu.tw/papers/HorngCS/JGSC2000_MD972143.pdf)
PHILIPPINE GEOLOGY AND MINERALIZATION: AN OVERVIEW
The
Philippines may be viewed as a collage of metamorphic terranes,
magma tic arcs, ophiolitic complexes, sedimentary basins and
continental block of Eurasian affinity subjected to tectonic
processes such as subduction, collision and major strike slip
faulting. The subduction zones are represented on the east by the
west dipping Philippine Trench traversing the eastern seaboard of
the Philippines from Mindanao up to a point in Luzon and the East
Luzon Trough. East dipping subduction zones include the Manila
Trench, Negros Trench and Cotabato Trench. The southern termination
of the Manila Trench is characterized by the transformation of the
subduction of the South China Sea Plate into an arc-continent
collisional deformation within Mindoro Island.
The
continental block is represented by northern Palawan, southern
Mindoro, Romblon Island Group and Buruanga Peninsula in Panay
Island, known collectively as the North Palawan Block. Rock suites
in this block include schists that are characteristically rich in
quartz and chart formations that have been dated Late Permian to
Jurassic.
The
rest of the archipelago is considered as the Philippine Mobile Belt.
Approximately co-axial with the mobile belt is the Philippine Fault,
a major strike slip fault that apparently developed partially in
response to the kinematic forces from the subduction from the east
and west of the mobile belt.
Many
areas of this mobile belt are underlain by ophiolitic complexes.
Usually occurring together with pre-Cenozoic schists and phyllites,
the ophiolitic rocks represent basement on which magma tic arcs have
developed. The ages of the ophiolitic complexes range from Jurassic
to early Paleogene. One of the best studied complete ophiolite
sequence is the Zambales Ophiolite where tectonized peridotites
progress to layered and isotropic gabbro, sheeted dike complex,
pillow basalts and finally pelagic sedimentary rocks. Other
ophiolitic complexes include those in Isabela, Polillo Island,
eastern Rizal, Camarines Norte, Caramoan Peninsula, Mindoro,
southern Palawan, Panay Island, Bohol Island, Leyte Island, Samar
Island, Dinagat Island Group, north-central Zamboanga, Mindanao
Central Cordillera and Pujada Peninsula. Ultramafic rocks of these
ophiolites are hosts to significant deposits of chromite and nickel.
Laterites over these rocks also contain economic deposits of
secondary nickel minerals. On the other hand, massive sulphide and
manganese deposits are associated with the volcanic and sedimentary
carapace of the ophiolite.
Ancient
magma tic arcs in the mobile belt are characterized by thick
volcanic flows intercalated with pyroclastic and sedimentary rocks
and intrusions of diorite, quartz diorite and andesitic to dacitic
rocks. Some intrusions, however, have a more alkalic character such
as the syenites in Isabela and monzonites in Quirino and Nueva
Vizcaya. The ages of the diorite intrusions vary, from late Early
Cretaceous (Albian) in Cebu to Late Miocene-Pliocene (Black Mountain
Quartz Diorite in Baguio District). Younger volcanic rocks,
occurring as flows, intrusions and volcanic edifices disposed in
linear belts are associated with active subduction processes. These
are best exemplified by the Bataan volcanic belt and Bicol volcanic
chain.
Sedimentary basins located between arcs include the Ilocos-Central
Valley Basin, Cagayan Valley Basin, southeast Luzon Basin, Visayan
Sea Basin, Agusan-Davao Basin and Cotabato Basin.
Gold
and copper deposits in the Philippines tend to be clustered in
certain areas such as Luzon Central Cordillera, Camarines Norte,
Surigao and Davao, although large deposits may also be found
elsewhere, as in Zambales (Dizon mine), Cebu (Atlas mine) and South
Cotabato (Tampakan project). Many copper-gold deposits are
associated with intrusions (mostly diorite and quartz diorite, but
also monzonites and syenites) as well as Pliocene – Pleistocene
volcanism (Lepanto mine at Mankayan, Benguet). Iron deposits are
also associated with Neogene intrusions of diorite and quartz
diorite.
(http://www.mgb.gov.ph/miningportal/geology/Geology.pdf)