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Monazite Meaning

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Monazite is a rare-earth element-rich phosphate mineral that is predominantly reddish-brown in colour. 

Monzite Formula: The Monazite formula is (Ce,La,Nd,Th)(PO4,SiO4) and in igneous and metamorphic rocks such as granite, pegmatite, schist, and gneiss, it is contained in small isolated grains as an accessory mineral. These grains withstand weathering and accumulate in soils and sediments downslope from the host rock. They are mined for their rare earth and thorium content when they reach high enough concentrations.  

Monazite price per ton- Monazite costs currently range from1680 to1900 per ton-1.


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Is Monazite Mineral or a Group of Minerals?

Monazite chemical formula is (Ce,La,Nd,Th)(PO4,SiO4), which indicates that cerium, lanthanum, neodymium, and thorium can all substitute for one another in the mineral's structure, as well as silica for phosphate. Monazite is a mineral that is found in a number of solid-solution series with other minerals.

The term "monazite" also refers to a group of monoclinic phosphate and arsenate minerals with similar compositions and crystal structures. Below is a list of minerals that belong to the monazite group. It's worth noting that monazite comes in a variety of forms.


Monazite Mineral Groups

Monazite Mineral Groups

Monazite Mineral

Monazite Chemical Formula

Brabantite

CaTh(PO4)2

Cheralite

(Ca,Ce,Th)(P,Si)O

Gasparite-(Ce)

(Ce,La,Nd)AsO4

Monazite-(Ce)

CePO4

Monazite-(La)

LaPO4

Monazite-(Nd)

NdPO4

Monazite-(Sm)

SmPO4

Rooseveltite

BiAsO4


Physical Properties of Monazite

Monazite is a resinous to vitreous mineral with a yellowish-brown to reddish-brown or greenish-brown lustre. It's transparent, and big grains or well-formed crystals are uncommon. Where monazite is abundant locally, granular masses can be seen. It has a cleavage that is pleasant and distinct. It has a hardness of 5 to 5.5. It has a high specific gravity that varies between 4.6 and 5.4 depending on its composition.


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Properties of Monazite

Physical Properties of Monazite

Chemical Classification

Phosphate

Colour

Yellowish to reddish-brown, greenish

Streak

White

Luster

Resinous, waxy, vitreous

Diaphaneity

Translucent

Cleavage

Good to poor

Mohs Hardness

5 to 5.5

Specific Gravity

4.6 to 5.4 (varies greatly depending upon rare earth type and concentration)

Diagnostic Properties

Specific gravity

Chemical Composition

(Ce,La,Nd,Th)PO4

Crystal System

Monoclinic


Geological Occurrence of Monazite Mineral

Monazite is known for its accumulation rather than its formation. It forms when igneous rocks crystallize and clastic sedimentary rocks metamorphose. Monazite, one of the most resistant minerals, concentrates in the weathering debris as these rocks weather. Monazite concentrations in soils and sediments near weathering outcrops can be higher than in the source rock.

The liberated monazite grains then begin their descent. They are eventually taken to a stream or a dry wash. Gravity and running water aid in the separation of hard grains of monazite and other heavy minerals from lighter minerals. They collect behind boulders, on the inside bends of stream channels, and eventually work their way down into the sediment deposit's lower levels. Any of them flow into the sea and settle in deltaic, beach, or shallow water sediments.


Monazite Mineral Mining

Monazite mining is concentrated in placer deposits since they are easier to mine and contain higher concentrations of monazite than hard rock deposits. Gold, silver, magnetite, ilmenite, rutile, zircon, and a number of gemstones are all heavy minerals that accumulate with monazite. The recovered heavy sands are extracted to extract the heavy minerals, with the light fraction being returned to the deposit. Heavy minerals have been dredged from stream sediments, alluvial terraces, coastal sediments, beach terraces, and shallow-water sediments.

The offshore waters of India, Malaysia, Vietnam, and Brazil now contain the majority of the world's monazite. The most extensive offshore monazite deposits are found in southern India and Sri Lanka. Australia was once the world's largest producer of monazite, and its monazite reserve is considered to be the world's largest. It hasn't been a major producer since the 1990s when public opposition forced the closure of mining on Frasier Island.

In the United States, monazite is not actually mined. It was previously mined in Idaho from stream placer deposits. The Idaho batholith weathered to form these deposits. Monazite was also extracted as a byproduct from offshore deposits along the United States' southeast coast, from North Carolina to Florida. Many states have inland and offshore reserves, but they are small and low-grade as compared to what is currently extracted in other countries.


Monazite Mineralization and Extraction

When released by the weathering of pegmatites, monazite minerals accumulate in alluvial sands due to their high density. Other heavy minerals of commercial interest, such as zircon and ilmenite, can be found in these so-called placer deposits, which are mostly sandy or fossil beach sands. Using gravity, magnetic, and electrostatic separation, monazite can be isolated as a nearly pure concentrate.

The monazite-(Ce) composition is invariably found in monazite sand deposits. In such monazites, the lanthanides usually contain 45–48 percent cerium, 24 percent lanthanum, 17 percent neodymium, 5 percent praseodymium, and trace amounts of samarium, gadolinium, and yttrium. Europium concentrations are typically low, averaging about 0.05 percent. The Lindsay Chemical Division of American Potash and Chemical Corporation, at the time the world's largest producer of lanthanides, extracted South African "rock" monazite from Steenkampskraal in the 1950s and early 1960s.

The full collection of lanthanides was available from the Steenkampskraal monazite. Monazite’s extremely low concentrations of the heaviest lanthanides justified the term "rare" earth for these elements, which came with correspondingly high costs. Monazite's thorium content varies, but it can reach 20–30% in some cases. Monazite derived from some carbonatites or tin ore veins in Bolivia is practically thorium-free. Commercial monazite sands, on the other hand, usually contain 6 to 12 percent thorium oxide.


1. Acid Cracking-

The initial method for extracting thorium and lanthanide from monazite was to heat it with concentrated sulfuric acid for several hours at temperatures between 120 and 150 °C. Several different methods to isolate thorium from the lanthanides were developed as a result of variations in the acid-to-ore ratio, the degree of heating, and the amount of water applied afterward. One of the processes caused the thorium to precipitate out in the crude form as phosphate or pyrophosphate, leaving a solution of lanthanide sulphates from which the lanthanides could be quickly precipitated as double sodium sulphate. The acid methods resulted in a significant amount of acid waste and a lack of phosphate content in the ore.


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2. Alkaline Cracking- 

A more recent method employs a hot sodium hydroxide solution (73 percent) at a temperature of about 140 °C. The valuable phosphate content of the ore can be recovered as crystalline trisodium phosphate using this method. After treating the lanthanide/thorium hydroxide mixture with hydrochloric acid, a solution of lanthanide chlorides and an insoluble sludge of the less basic thorium hydroxide is obtained.


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Monazite Uses

  • Monazite is an important source of thorium, cerium, and other rare elements.

  • It is often mined as a byproduct of heavy mineral deposits.

  • Monazite sand is used in construction and casting. 

FAQ (Frequently Asked Questions)

1. Where Can We Find Monazite in India? What is the Formula of Monazite?

Ans. Monazite sands can be found on the east and west coasts, as well as in some areas of Bihar. However, the Kerala coast has the highest concentration of monazite sand. Monazite is thought to contain over 15,200 tonnes of uranium. The copper mines of Udaipur, Rajasthan, contain some uranium.


The Formula of Monazite is (Ce,La,Nd,Th)(PO4,SiO4).

2. Which Mineral is Contained in Monazite Sand?

Ans. In the Kerala sands, monazite sands are made up of phosphate minerals containing elements like cerium, which appear as small brown crystals (these monazite sands are mined for both cerium and radioactive thorium oxide).

3. Which State of India Has the Largest Reserve of Monazite?

Ans. Kerala's soil is acidic, with a high phosphate capacity and low water holding capacity, and it has India's largest monazite reserves.

4. Why are the Monazite Sands in Kerala Useful?

Ans. Earth metals, thorium, lanthanum, and cerium are abundant in the monazite sands of Kerala. Monazite can be radioactive due to the presence of thorium within it. Monazite contains a large amount of helium, which can be removed by heating due to the alpha decay of thorium and uranium.