Fertiliser minerals  
     
  A phosphorite or phosphate rock is a non-detrital sedimentary rock which contains high amounts of phosphate bearing minerals. The phosphate content of phosphorite is at least 20% which is a large enrichment over the typical sedimentary rock content of less than 0.2%. The phosphate is present as fluorapatite typically in cryptocrystalline masses (grain sizes < 1 µm) referred to as collophane. The dark brown to black beds range from a few centimetres to several metres in thickness. The layers contain the same textures and structures as fine grained limestones and may represent diagenetic replacements of carbonate minerals by phosphates.

Potash (or carbonate of potash) is an impure form of potassium carbonate (K2CO3).

Potash has been used since antiquity in the manufacture of glass and soap and as a fertilizer. The name comes from the English words pot and ash, referring to its discovery in the water-soluble fraction of wood ash.

The term has become somewhat ambiguous due to the substitution in fertilizers of cheaper potassium salts, such as potassium chloride (KCl) or potassium oxide (K2O) , to which the same common name is now sometimes also applied. In addition, potassium hydroxide (KOH) is commonly called caustic potash, an additional source of confusion.

 
     
 
Common name Chemical name Formula
Potash fertilizer potassium oxide K2O
Caustic potash or potash lye potassium hydroxide KOH
Carbonate of potash, salts of tartar, or pearlash potassium carbonate K2CO3
Chlorate of potash potassium chlorate KClO3
Muriate of potash potassium chloride KCl
Nitrate of potash or saltpeter potassium nitrate KNO3
Sulfate of potash potassium sulfate K2SO4
Permanganate of potash potassium permanganate KMnO4
 
     
  RESOURCES IN INDIA  
     
  i) Phosphorite (Rock Phosphate)
The all India total resources as on 1-4-2005 (provisional) are 309.22 million tonnes of which 17.12% are under Reserve category and 82.88% under Remaining Resource category. Gradewise total resources are chemical/fertilizer (6.83%), blendable (9.24%), soil reclamation (11.66%), beneficiable (30.26%), low grade (35.53%) and remaining 6.48% are under others, unclassified and not known grades.Out of the total resources, 44.38% are leasehold and 55.62% under freehold. Out of total resources of 137.2 million tonnes are under leasehold, public sector accounting for 95.56% and remaining 4.44% in private sector. Under leasehold 6.95% are in captive and remaining 93.05% in non-captive sector. Rock phosphate is an important fertilizer mineral, which is in short supply. Inspite of country’s production of around one million tonnes, India is deficient in this mineral and bulk of the requirement are met by imports.

Phosphate deposits are confined to Proterozic sedimentary rocks located in Udaipur district of Rajasthan; Jhabua, Sagar and Chattarpur districts of Madhya Pradesh and Maldeota belt of Uttaranchal and Lalitpur districts of Uttar Pradesh. Potential apatite deposits are located in Purulia district of West Bengal and Singhbhum district of Jharkhand.

Phosphorites associated with Aravalli are located at Jhamarkotra, Maton and Kanpur in Udaipur district, Rajasthan. Jhamarkotra is the biggest deposit located so far. In Rajasthan, other phosphorite deposits are reported from Banswara, Udaipur, Jaipur and Jaisalmar districts. In Madhya Pradesh, important deposits are in Jhabua, Sagar and Chhattarpur districts. In Uttar Pradesh deposits are located in Lalitpur district. In Uttaranchal these are located in Dehradun and Tehri Garhwal districts. Phosphorite deposits are also located in Panchamahal district of Gujarat and Palamu district of Jharkhand.

 
     
  ii) Potash:
Deep seated bedded potash mineralization has been located in Nagaur district of Western Rajasthan. The amenability of these deposits to conventional mining/solution mining is not established.

Occurrences of potash and potash rich brines are in J&K and Gujarat. Saltpetre type of potash is found on the soil surface in Punjab, U.P., A.P. and Tamil Nadu. Glauconite occurring in Gujarat, Rajasthan and Madhya Pradesh have poor grade of potash.

The all India total resources of potash as on 1-4-2005 (provisional) are 21,815 million tonnes, all under Remaining Resource Category. Gradewise 1,946 million tonnes are glauconite 16,164 million tonnes are polyhalite, 2,477 million tonnes sylvite and 1,228 million tonnes are unclassified. All the resources are in freehold. Deep seated bedded sylvite mineralisation has been located in Nagaur district of Western Rajasthan accounting practically for entire resources. GSI has carried out the exploration by drilling in Nagaur/Sri Ganganagar basin of Rajasthan and has estimated about six trillion tonnes of halite containing about 80% NaCl over an area of 40,000 Sq. km.

Western Rajasthan holds good potential for potash deposits. The K-rich mineralisation is very deep seated with thickness of overburden ranging from 593 to 676 m and feasibility of mining is yet to be established. The underground brine in Runn of Kutch is also a potential source of potash.