Chunks of cloudstone can even take you longer to get than Pure Bladestone.
Demon's Souls forums and on gamefaqs have people who reached the conclusion that Chunks of Cloudstone are a glitchy drop.
Unless you have 99 Shards of Cloudstone on both Stockpile Thomas and on yourself, the drop rate of Chunks are about 1 per hour or so. Given the possibility that you may need 6 of them, you'll be in for about 6 hours of farming, if you get lucky and have that drop rate, because I was having a Chunk dropping at about 2 hours per Chunk.
That was until I farmed the 99s as I said to you, then I got a Chunk for every 15 minutes of farming. Don't know why this is the case, but lot's of people have had the same problem and the same trick has worked with them.
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