Given the task definition and input, reply with output. In this task, you're given passages that contain mentions of names of people, places, or things. Some of these mentions refer to the same person, place, or thing. Your job is to write questions that evaluate one's understanding of such references. Good questions are expected to link pronouns (she, her, him, his, their, etc.) or other mentions to people, places, or things to which they may refer. Do not ask questions that can be answered correctly without understanding the paragraph or having multiple answers. Avoid questions that do not link phrases referring to the same entity. For each of your questions, the answer should be one or more phrases in the paragraph, and it should be unambiguous.

Passage: The Rosetta Stone is listed as "a stone of black granodiorite, bearing three inscriptions ... found at Rosetta" in a contemporary catalogue of the artefacts discovered by the French expedition and surrendered to British troops in 1801. At some period after its arrival in London, the inscriptions on the stone were coloured in white chalk to make them more legible, and the remaining surface was covered with a layer of carnauba wax designed to protect the Rosetta Stone from visitors' fingers. This gave a dark colour to the stone that led to its mistaken identification as black basalt. These additions were removed when the stone was cleaned in 1999, revealing the original dark grey tint of the rock, the sparkle of its crystalline structure, and a pink vein running across the top left corner. Comparisons with the Klemm collection of Egyptian rock samples showed a close resemblance to rock from a small granodiorite quarry at Gebel Tingar on the west bank of the Nile, west of Elephantine in the region of Aswan; the pink vein is typical of granodiorite from this region.The Rosetta Stone is 1,123 millimetres (3 ft 8 in) high at its highest point, 757 mm (2 ft 5.8 in) wide, and 284 mm (11 in) thick. It weighs approximately 760 kilograms (1,680 lb). It bears three inscriptions: the top register in Ancient Egyptian hieroglyphs, the second in the Egyptian Demotic script, and the third in Ancient Greek. The front surface is polished and the inscriptions lightly incised on it; the sides of the stone are smoothed, but the back is only roughly worked, presumably because this would have not been visible when it was erected.
How many kilograms does the Rosetta Stone weigh?