The third island, which is surrounded by an ocean of clarified butter and is also divided into seven regions, is called Kuśadvīpa. Its master is Hiraṇyaretā, another son of Mahārāja Priyavrata, and its inhabitants worship the Supreme Personality of Godhead in the form of Agni, the fire-god. The width of this island is 6,400,000 miles, or, in other words, twice the width of Sālmalīdvīpa.
(Srimad Bhagavatam------5:20------summary).

Outside the ocean of liquor is another island, known as Kuśadvīpa, which is 800,000 yojanas [6,400,000 miles] wide, twice as wide as the ocean of liquor. As Śālmalīdvīpa is surrounded by a liquor ocean, Kuśadvīpa is surrounded by an ocean of liquid ghee as broad as the island itself. On Kuśadvīpa there are clumps of kuśa grass, from which the island takes its name. This kuśa grass, which was created by the demigods by the will of the Supreme Lord, appears like a second form of fire, but with very mild and pleasing flames. Its young shoots illuminate all directions.
(Srimad Bhagavatam------5:20:13------translation).

Outside the ocean of clarified butter is another island, known as Krauñcadvīpa, which has a width of 1,600,000 yojanas [12,800,000 miles], twice the width of the ocean of clarified butter. As Kuśadvīpa is surrounded by an ocean of clarified butter, Krauñcadvīpa is surrounded by an ocean of milk as broad as the island itself. On Krauñcadvīpa there is a great mountain known as Krauñca, from which the island takes its name.
(Srimad Bhagavatam------5:20:18------translation).

The ground at the foot of the mountain is always washed by waves of milk that produce emeralds all around in the eight directions [north, south, east, west and the directions midway between them]. From Śrīmad-Bhāgavatam we understand that there are various oceans. Somewhere there is an ocean filled with milk, somewhere an ocean of liquor, an ocean of ghee, an ocean of oil, and an ocean of sweet water. Thus there are different varieties of oceans within this universe. The modern scientists, who have only limited experience, cannot defy these statements; they cannot give us full information about any planet, even the planet on which we live. From this verse, however, we can understand that if the valleys of some mountains are washed with milk, this produces emeralds. No one has the ability to imitate the activities of material nature as conducted by the Supreme Personality of Godhead.
(Srimad Bhagavatam------8:2:4------translation and purport).