<p>According to TibiaFandom:</p><table cellpadding="1" border="1" style="height:255px; width:728px; border-spacing: 1px;"><tbody><tr><td width:728px"><tbody><tr><td style="text-align:center"><strong>item</strong></td><td style="text-align:center"><strong>amount</strong></td><td style="text-align:center"><strong>percentage</strong></td><td style="text-align:center"><strong>tries to get 1</strong></td></tr><tr><td><img alt="Crate Full of Coral.gif" src="https://static.wikia.nocookie.net/tibia/images/6/62/Crate_Full_of_Coral.gif/revision/latest/scale-to-width-down/32?cb=20140125105052&path-prefix=en" src="https://vignette.wikia.nocookie.net/tibia/images/6/62/Crate_Full_of_Coral.gif/revision/latest/scale-to-width-down/32?cb=20140125105052&path-prefix=en" style="height:32px; width:32px"><em>You manage to mine enough chunks of coral to fill one crate</em></td><td>121</td><td>9,7%</td><td>11</td></tr><tr><td><img alt="Deepling Worker.gif" src="https://static.wikia.nocookie.net/tibia/images/8/8a/Deepling_Worker.gif/revision/latest/scale-to-width-down/64?cb=20171218214540&path-prefix=en" src="https://vignette.wikia.nocookie.net/tibia/images/8/8a/Deepling_Worker.gif/revision/latest/scale-to-width-down/64?cb=20171218214540&path-prefix=en" style="height:64px; width:64px"> <span style="color:null"><em>It seems you disturbed a Deepling worker.</em></span></td><td>776</td><td>62,18%</td><td>2</td></tr><tr><td><em>The coral you mined was crumbly and of minor quality.</em></td><td>351</td><td>28,13%</td><td>4</td></tr></tbody></table><p>soure: <a rel="nofollow" href="https://tibia.fandom.com/wiki/Liquid_Black_Quest">https://tibia.fandom.com/wiki/Liquid_Black_Quest</a></p><p>Unfortunately the only source with this kind of information you can find on Wiki, which is created by players and we can not consider it as official info, however amount of tries seems to be high enough to identify helpful statistics.</p><p>From my own experience I can say that gatherigh 10 Crates Full of Coral <a rel="nofollow" href="https://static.wikia.nocookie.net/tibia/images/6/62/Crate_Full_of_Coral.gif/revision/latest?cb=20140125105052&path-prefix=en"><img alt="Crate Full of Coral.gif" src="https://static.wikia.nocookie.net/tibia/images/6/62/Crate_Full_of_Coral.gif/revision/latest/scale-to-width-down/32?cb=20140125105052&path-prefix=en" src="https://vignette.wikia.nocookie.net/tibia/images/6/62/Crate_Full_of_Coral.gif/revision/latest/scale-to-width-down/32?cb=20140125105052&path-prefix=en" style="height:32px; width:32px"></a> takes about 30-45 minutes.</p>