Carbonate ore of iron is Siderite.

Explanation:
Siderite is a mineral composed of iron carbonate (FeCO3). It is a valuable iron mineral and is also known as "ironstone" or "iron spar." Siderite is found in various geological environments and is an important source of iron.

Properties of Siderite:
- Chemical Formula: FeCO3
- Crystal System: Trigonal
- Color: Yellowish, brownish, grayish, greenish
- Hardness: 3.5-4.5 on the Mohs scale
- Cleavage: Perfect in three directions forming rhombohedrons
- Luster: Vitreous to pearly
- Specific Gravity: 3.96-4.1

Occurrence:
Siderite is commonly found in sedimentary rocks, particularly in banded iron formations. It often occurs as concretions or nodules within the rock layers. These nodules can be quite large and are often referred to as "siderite pseudo-spheres."

Uses:
- Iron Ore: Siderite is an important source of iron ore. It can be processed to extract iron and used in the production of steel.
- Pigments: Siderite has been used as a pigment in paints and dyes due to its yellowish-brown color.
- Jewelry: Siderite is sometimes used as a gemstone and is cut into cabochons or used in jewelry in its natural form.

Other Carbonate Ores of Iron:
While siderite is the primary carbonate ore of iron, there are other carbonate minerals that contain iron as well. These include:
- Calamine (ZnCO3): Calamine is a zinc carbonate ore that can sometimes contain small amounts of iron impurities.
- Carnalite (KMgCl3·6H2O): Carnalite is a potassium magnesium chloride mineral that does not contain iron, but it is sometimes associated with iron-rich sedimentary deposits.
- Galena (PbS): Galena is a lead sulfide ore and does not contain iron carbonate.

In conclusion, the correct answer is option B - Siderite. Siderite is a carbonate ore of iron and is an important source of iron for various industrial applications.