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According to Chemistry LibreText:

Lithium is the lightest of all metals and is named from the Greek work for stone (lithos). It is the first member of the Alkali Metal family. It is less dense than water (with which it reacts) and forms a black oxide in contact with air.

However, if I'm not wrong, all alkali-metals react with non-metals to form white oxides. $\text{Li}_2 \text{O}$ is a white chemical compound, isn't it? What's with the site stating the opposite -- anything I'm possibly missing out on?

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    $\begingroup$ It is white, as you say. The black stuff, as per wikipedia, is several substances. $\endgroup$
    – Ed V
    Aug 24, 2021 at 13:04
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    $\begingroup$ Aldrich sell Lithium Oxide as a "white crystalline solid" sigmaaldrich.com/GB/en/product/aldrich/374725 $\endgroup$
    – Waylander
    Aug 24, 2021 at 13:37
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    $\begingroup$ One has to remember lithium reacts with nitrogen as well. $\endgroup$
    – Poutnik
    Aug 24, 2021 at 14:15

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From Handbook of Inorganic Chemicals by Pradyot Patnaik:

LITHIUM OXIDE

White cubic crystals; refractive index $\pu{1.644}$; density $\pu{2.013 g/cm3}$; melts at $\pu{1,570 °C}$; dissolves and decomposes in water ($\pu{6.67 g/100g}$ at $\pu{0 °C}$ and $\pu{10.02 g/100g}$ at $\pu{100 °C}$).

What the quote has written is not correct. Lithium on contact with air forms both lithium oxide and lithium nitride which looks black during the reaction perhaps due to constant oxidation (actually pure lithium nitride exist as red hexagonal crystals). The reaction is exothermic.

$$\ce{6Li + N2 -> \underset{black}{2Li3N}}$$

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