CHROMITE Flashcards
Chromite chem formula
FeCr2O4
Depending on the chrome to iron ratio (Cr:Fe), chromite ores can be classified according to their use as
Metallurgical (2.4-3.2:1)
Refractory (1.8-2.3:1)
Chemical (lower Cr:Fe ratios)
In stainless steels, chromium makes up ____ or more of the final
composition
10%
Hardness and Specific gravity of chromium
5.5 and 4.5 - 4.8
The early discoveries of chromite deposits in Ilocos Norte; Ambil Island, Mindoro; and Antique, Panay as well as the chromite-rich laterite deposits in Surigao were
reported by _________ who was the Chief of the Division of Mines of the Bureau of Soil from 1907 to 1914.
Warren D. Smith
In a geological reconnaissance survey of the Zambales Range done by the same bureau in 1925, the largest chromite deposit in the country was discovered along
_____ about 24 km east of Masinloc.
Lawis River (10 to 15 MT with 30%-37% Cr2O3 grade)
It was only in 1934 when chromite mining started and was followed a year later by the first ore shipment from _____ in Lagonoy, Camarines Sur.
Floranie Mines
In the following years up to 1997, the demand for chromite continued to fluctuate but definitely showed downtrend production that may be attributed to:
(i) exhaustion of
some Philippine deposits;
(ii) discovery of bigger deposits in other countries, thereby
(iii) lowering the global price of chromite and making many deposits of subeconomic grade; and, most recently,
iv) slackening of the global economy.
The foremost producers of refractory and metallurgical chromite are
Masinloc Chromite Operations (Benguet Corporation) and Krominco, Inc. Heritage Resources and Mining Corporation
The regional distribution of chromite occurrences can be delineated in terms of the
recognized ________ that characterize the Philippine island-arc system.
Ophiolite belts
Chromite distribution in recognized ophiolitic belts
1) Zambales Ophiolite;
2) Casiguran Ophiolite;
3) Angat Ophiolite;
4) Eastern Bicol-Eastern Mindanao
Ophiolite;
5) Western Bicol-Eastern Leyte Ophiolite;
6) Central Mindanao Ophiolite;
7) Antique Ophiolite;
8) Zamboanga-Sulu Ophiolite; and 9) Palawan Ophiolite
The ophiolite-associated chromite occurrences are classified as __________ or ______ deposits
podiform or Alpinetype
This zone is characterized by the non-systematic distribution of chromite bodies within the harzburgite section showing no clear relationship between the size of the deposit and the extent or thickness of the enclosing dunite selvage.
Zone 1 in harzburgite
A 200-500 meter zone of dominantly dunitic layer occurring immediately below the mafic-ultramafic cumulate section
characterizes this zone. The chromite and dunite bodies are believed to be of residual mantle materials. Most of the metallurgical and refractory chromite deposits are associated with this dunite horizon. Chromites in this section can also be viewed as products of
melt – rock interaction between the more evolved ascending magma along mantle conduits with that of the mantle wall rocks
Zone 2 in upper level dunite
This is characterized by
concordant to subconcordant chromite bands or lenses occurring within a 100 -500 meters interlayered dunite-wehrlite sequence, representing the base of the cumulate gabbro section. This zone is also conceived to be the petrological crust-mantle transition.
Zone 3 in interlayered dunite and wehrlite
secondary minerals in association with chromite include
antigorite, talc, chrysotile, actinolite, tremolite, sepiolite, kammererite, magnesite, clinochlore, penninite, brucite, fuchsite, uvarovite, and limonite
These deposits form through secondary processes such as residual weathering and mechanical weathering and transport. They are found as alluvial/lateritic or beach and sand placer deposits. Laterite deposits occur as a soul veneer over ultramafic rocks in various locations, with chromite-bearing black sands found in alluvial fans and beaches.
Residual and Transported Chromite
Commercial chromite ores must contain more than ___ Cr2O3 to the considered suitable for industrial applications
45%
43% - 45% for chemical grade ores
Cr:Fe ratio for commercial ores
Metallurgical Grade (2.5:1)
Refractory Grade (2.5:2)
Chemical (1.6:1)
Acoje Mining Corp.
- Acoje orthomagmatic podiform chromite deposit
- Pascal, Sta. Cruz, Zambales
- Acoje mafic ultramafic block
- 1997-98 with 6127 DMT.
Consolidated
Mines, Inc. and operated by Benguet Corporation
- Coto orthomagmatic podiform chromite deposit
- Brgy. Baloganan, Masinloc, Zambales
- Coto Block of the Zambales Ophiolite
- 1997-2000 with 138,178 DMT
Krominco, Incorporated
- Krominco orthomagmatic stratiform deposits
- Western slopes of Mt. Redondo,
northern Dinagat Island, Surigao del Norte - Dunite unit of Dinagat ophiolite
- 1997-2000 with 61,439 DMT
Pacific Shore Mining and Rio Chico Mining corporations
- Samar lateritic (residual) chromite deposit- Western slopes of Mt. Redondo,
- Samar
- Cretaceous metavolcanic rocks (Camcuevas and Calicoan formation)
- 15,000 MT concentrates per year.
Philcrome Mining Corporation
- Batang-Batang alluvial chromite and chromite sand deposit
- Palawan
- Quaternary beach sediments
Major Uses of chromium
- Chromium plating- decorative purposes, especially as body trim on automobiles
- Pigments and dyes- pigments and mordant to fix dyes enhances durability and color stability
- Refractories – use to line furnaces capitalizing on chromium’s high melting point and stability under extreme temperatures
