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While the reasons for it's existence do not matter as it is part of an artificially created planet, I am curious if a lapis lazuli island would be able to survive erosion and support Earth-like life? Are there any new dangers that would come about from this kind of environment? What kind of adaptions would be likely in such a place?

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    $\begingroup$ "Survive erosion" for how long? Nothing survives erosion indefinitely. Lapis is at least as hard as the hardest marble, and much harder than the chalk of which the White Cliffs of Dover are made. Now an island made entirely of rock may is a challenging environment. Trees don't grow on rock, grass doesn't grow on rock. There may be lichens, sea birds, seals... $\endgroup$
    – AlexP
    Commented Feb 2, 2018 at 12:58
  • $\begingroup$ @AlexP Long enough that it would survive long enough that it could be inhabited. If it is as resistant as you say, that part of the problem is pretty much solved. $\endgroup$ Commented Feb 2, 2018 at 13:07
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    $\begingroup$ It would essentially be a monolith. If the top is flat there might be enough soil for plants. In any case plants do not grow directly on stone, so ecology would be derived from how much soil and water is collected on top of the stone, which depends on the shape. $\endgroup$ Commented Feb 2, 2018 at 13:07
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    $\begingroup$ The real reason this exists is to mine it to boost your enchanting tables. $\endgroup$
    – DonielF
    Commented Feb 2, 2018 at 17:00

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Its not too much different from obsidian

First off, lapis lazuli is a gemstone mostly formed of the mineral lazurite. Lazurite has the same blue appearance as lapis lazuli, so it might be more reasonable (and accurate) to say that your island is made of lazurite.

Based on lazurite's hardness (5-5.5 on the Mohs scale) and density (~2400 kg/m$^2$); it probably wouldn't act that much differently from obsidian (hardness 5-6, density ~2400 kg/m$^2$). Obsidian lava flows are not too inhospitable for life, other than the fact that they are bare rock. There is plenty of documentation about how obsidian lava flows can be overgrown with plants in a matter of decades.

Obviously, a primary difference between lazurite and obsidian that the soil derived from this island would be blue. Ground up lapis lazuli is an expensive painting pigment called ultramarine; your islands soil would be pigment mixed with organic matter.

Lazurite has an interesting mix of minerals in it, with sodium, calcium, and sulfate content that will be good for plants. However, without phosphates and nitrates, it might be a hard for plants to get a head start. On the other hand, seabird guano's fertilizing properties are primarily in teh form of ammonium nitrate and phosphates. A few hundred thousand years of seabirds nesting on the bare rock might provide all the soil nutriment needed for the place to be over-run with vegetation.

I don't see lazurite being called alkali anywhere specifically, but it is a feldspathoid mineral, and many of these minerals are alkali. So it seems likely that your soil will have a high pH, which may limit the plants that can colonize. Volcanic derived soils are usually acidic, by contrast. However, in keeping with the seabird island theme, coconut palms will do fine up to pH of 9 (and maybe higher) so plant life would be able to get a start on such an island, even if it has an alkaline soil.

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    $\begingroup$ Hmm... would the potency of the pigment lead to unusual coloration of the organisms on the island? $\endgroup$
    – Tin Wizard
    Commented Feb 2, 2018 at 18:59
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    $\begingroup$ I don't think so. The colour is from sulphide (III) ions, rather than a heavy metal. The sulphur would likely get moved to another oxidation state as it moved into the organisms, so the blue colour likely wouldn't survive. Other oxidation states aren't strongly coloured. $\endgroup$ Commented Feb 2, 2018 at 19:34
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    $\begingroup$ @user1908704 the ion is actually S3 single minus , so the average oxidation state is one third, not three. $\endgroup$ Commented Feb 2, 2018 at 21:07
  • $\begingroup$ "Without phosphates and nitrates, it might be hard for plants to get a head start" — or it could be that there would be plants evolved with completely different biochemical properties. Larry Niven's novel "Destiny's Road" comes to mind. $\endgroup$
    – Wildcard
    Commented Feb 3, 2018 at 0:33

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