Which one among the following rocks does not belong to the same group?

Rocks are classified into three major types: igneous, sedimentary, and metamorphic. Shale, limestone, and sandstone are all classified as sedimentary rocks [2]. Specifically, shale and sandstone are clastic sedimentary rocks formed from the lithification of rock fragments, while limestone can be formed mechanically, organically, or chemically [2]. In contrast, slate is a metamorphic rock [3]. It is formed when existing sedimentary rocks, such as shale or clay, are subjected to intense heat and pressure, causing them to undergo physical and chemical changes [4]. Therefore, while shale, limestone, and sandstone belong to the sedimentary group, slate belongs to the metamorphic group, making it the odd one out [1].

Sources

1. [2] Physical Geography by PMF IAS, Manjunath Thamminidi, PMF IAS (1st ed.) > Chapter 13: Types of Rocks & Rock Cycle > 13.2. Sedimentary Rocks or Detrital Rocks > p. 171
2. [1] Physical Geography by PMF IAS, Manjunath Thamminidi, PMF IAS (1st ed.) > Chapter 13: Types of Rocks & Rock Cycle > Some Examples of Metamorphosis > p. 174
3. [3] Geography of India ,Majid Husain, (McGrawHill 9th ed.) > Chapter 6: Soils > Parent Material > p. 1
4. [4] Certificate Physical and Human Geography , GC Leong (Oxford University press 3rd ed.) > Chapter 2: The Earth's Crust > METAMORPHIC ROCKS > p. 19