III. Iron Flashcards
What is the luster of iron?
Lustrous
Is iron ductile or brittle?
Ductile
Is iron malleable or rigid?
Malleable
What color is iron in its pure form?
Silver-gray
What is the specific gravity range of iron?
7.3 – 7.87
What is the hardness of iron on the Mohs scale?
4.5
How does iron react to a magnet?
It is strongly attracted by a magnet.
What is the ranking of iron in terms of abundance among elements in the Earth’s crust?
4th most common element
Among metallic elements, where does iron rank in terms of abundance?
2nd most abundant metallic element
What is the shiny, metallic variety of Hematite called?
Specularite
What is the earthy, reddish variety of Hematite called?
Red Ochre
What is the chemical formula of Magnetite?
Fe₃O₄ (ferrous oxide)
Philippine iron deposits are classified into:
Skarn (or contact metasomatic), Magnetite sand, Laterite, Sedimentary, Bog, Spring
What is the chemical formula of Hematite?
Fe₂O₃ (ferric oxide)
Which iron mineral has the formula Fe₂O₃·3H₂O?
Limonite (ferric oxide trihydrate)
Which iron mineral commonly occurs as rhombohedral crystals and is often associated with sedimentary deposits?
Siderite
What iron mineral forms as a product of weathering and oxidation of iron-rich minerals?
Goethite
Which iron mineral is typically found in earthy, yellow-brown masses?
Limonite
Which iron mineral is known for its strong magnetic properties?
Magnetite
What is the chemical formula of Siderite?
FeCO₃ (ferrous carbonate)
What is the chemical formula of Goethite?
FeO·OH
What is the most important type of iron deposit in the Philippines?
Skarn
What geologic setting do iron skarn deposits in the Philippines occur in?
In a setting where limestone or calcareous sediments are intruded by a younger intermediate to acidic pluton.
Where is the skarn developed in relation to the intrusive contact?
Not far from the margins of the intrusive contact into the metasomatized limestone/calcareous sedimentary rock.
Which areas in the Philippines have notable iron skarn deposits besides Luzon and Mindanao?
Samar, Eastern Bicol, Mindoro, Marinduque, Buruanga Peninsula in Panay, Malangas-Sibuguey Islands
What does the age of iron skarn deposits reflect?
The age of the related intrusive rocks responsible for skarn formation.
What type of plutonic bodies are iron skarn deposits in the Philippines associated with?
Intermediate to acidic plutonic bodies
Name an island in the Visayas where iron skarn deposits are found.
Cebu, Guimaras Island, or Southwestern Negros
Which region in Mindanao is known for iron skarn deposits?
Eastern Mindanao and Daguma Range in Southern Mindanao
In which geological region of Luzon are iron skarn deposits found?
Central Cordillera
What other metals commonly occur with iron in skarn-type deposits?
Gold, copper, lead, and zinc.
What is the typical magnetite content in magnetite sand?
15 to 30% magnetite
What is the iron yield of concentrated magnetite sand?
55 to 60% Fe
What impurities in magnetite sand interfere with the smelting process?
Titanium and vanadium
How do impurities like titanium and vanadium affect magnetite sand during smelting?
They lower the quality of the iron ore
What type of mining is prohibited in the Philippines under Batas Pambansa Blg. 265?
Beach sand mining
Where are the most extensive magnetite sand deposits found in the Philippines?
Northern and northwestern Luzon, eastern Leyte, and southwestern Negros
When was Batas Pambansa Blg. 265 approved?
November 13, 1982
Which law prohibits the extraction of gravel and sand from beaches in the Philippines?
Batas Pambansa Blg. 265
What is the typical thickness of iron laterite deposits over mafic and ultramafic rocks?
10 to 15 meters
What types of rocks are associated with nickeliferous laterite deposits?
Ultramafic rocks (e.g., dunite and peridotite)
What mineral forms upon weathering of ultramafic rocks in nickeliferous laterite deposits?
Silicate nickel ore (garnierite)
What mineral forms where iron diminishes at depth in aluminous laterite deposits?
Bauxite or bauxitic clay
What types of rocks are associated with aluminous laterite deposits?
Mafic rocks (e.g., gabbro and basalt)
What are the two types of iron laterite deposits?
Nickeliferous and aluminous
Name a location in Luzon where major nickeliferous laterite iron deposits are found.
Northern Sierra Madre or Zambales Range
Name an island in the Visayas where major nickeliferous laterite iron deposits are located.
Sibuyan Island or southern Samar
Which island groups in Mindanao have major nickeliferous laterite iron deposits?
Dinagat Island Group and northern Surigao
Where are the only aluminous laterite iron deposits that have been explored in the Philippines?
Bucas Grande and Siargao islands in Surigao del Norte
How do sedimentary iron deposits typically occur?
As layers of hematite and/or magnetite interbedded with sediments.
Where are the only two known sedimentary iron deposits in the Philippines located?
Camalaniugan, Cagayan and Tinambac, Camarines Sur.
What is the geologic association of the sedimentary iron deposit in Camalaniugan, Cagayan?
Pliocene to Pleistocene clastics with hematite and magnetite as ore minerals.
What is the geologic association of the sedimentary iron deposit in Tinambac, Camarines Sur?
Cretaceous greywackes and spilitic lavas with hematite and minor magnetite and pyrolusite as ore minerals.
iron ores occur in small low-grade deposits with much
manganese, phosphorus, water, clay, and other impurities
Limonitic bog
What impurities are commonly found in sedimentary bog iron ores?
Manganese, phosphorus, water, clay, and other impurities
What causes the precipitation of ferric oxides and hydroxides in bog iron ores?
Bacterial action breaking down humic iron complexes and ferrous bicarbonate
How are iron supplies transported to bog waters?
by streams and springs
Where is a relatively important bog iron sedimentary deposit located in the Philippines?
Taan, Nueva Vizcaya
