Which one of the following ores is known as Malachite:

We are given a question about identifying the ore known as Malachite. Malachite is a common copper ore, and we need to recall its chemical composition.

Malachite is a green mineral that is a hydrated copper carbonate. Its chemical formula is Cu2CO3(OH)2. This can also be written as CuCO3 · Cu(OH)2 because Cu2CO3(OH)2 is equivalent to CuCO3 · Cu(OH)2. Let's verify this equivalence:

Starting with CuCO3 · Cu(OH)2:
This represents one molecule of copper carbonate and one molecule of copper hydroxide. Writing the atoms:
CuCO3 has Cu, C, and 3O.
Cu(OH)2 has Cu, 2O, and 2H (since OH is oxygen and hydrogen).
Combining: Cu + Cu = 2Cu; C = 1C; O: 3 + 2 = 5O; H: 2H.
So the combined formula is Cu2CO5H2. But note that CO3(OH)2 can be rewritten as CO3 and (OH)2, and in standard notation, Cu2CO3(OH)2 means two copper atoms, one carbonate group (CO3), and two hydroxide groups (OH)2, which is Cu2CO3(OH)2 and has the same atoms: 2Cu, 1C, 3O (from CO3) + 2O and 2H (from two OH groups) = 2Cu, 1C, 5O, 2H. Hence, CuCO3 · Cu(OH)2 is indeed equivalent to Cu2CO3(OH)2.

Now, let's examine the options:

Option A: Cu2S - This is copper(I) sulfide, known as Chalcocite, not Malachite.

Option B: Cu2O - This is copper(I) oxide, known as Cuprite, not Malachite.

Option C: Cu(OH)2 · CuCO3 - As established, this is the formula for Malachite.

Option D: CuFeS2 - This is copper iron sulfide, known as Chalcopyrite, not Malachite.

Therefore, the ore known as Malachite is Cu(OH)2 · CuCO3.

Hence, the correct answer is Option C.