 Four allotropes of antimony are known : a stable metallic form and three metastable forms ( explosive , black and yellow ) . Elemental antimony is a brittle , silver @-@ white shiny metalloid . When slowly cooled , molten antimony crystallizes in a trigonal cell , isomorphic with the gray allotrope of arsenic . A rare explosive form of antimony can be formed from the electrolysis of antimony trichloride . When scratched with a sharp implement , an exothermic reaction occurs and white fumes are given off as metallic antimony is formed ; when rubbed with a pestle in a mortar , a strong detonation occurs . Black antimony is formed upon rapid cooling of vapor derived from metallic antimony . It has the same crystal structure as red phosphorus and black arsenic , it oxidizes in air and may ignite spontaneously . At 100 ° C , it gradually transforms into the stable form . The yellow allotrope of antimony is the most unstable . It has only been generated by oxidation of stibine ( SbH3 ) at − 90 ° C. Above this temperature and in ambient light , this metastable allotrope transforms into the more stable black allotrope . 
 Four allotropes of antimony are known : a stable metallic form and three metastable forms ( explosive , black and yellow ) . Elemental antimony <a href='drop_aux' title='1'><mark>is</mark></a>a brittle , silver @-@ white shiny metalloid . When slowly cooled , molten antimony crystallizes in a trigonal cell , isomorphic with the gray allotrope of arsenic . A rare explosive form of antimony can be formed from the electrolysis of antimony trichloride . When scratched with a sharp implement , an exothermic reaction <a href='uninflect' title='2'><mark>occurs</mark></a> and white fumes are given off as metallic antimony is formed ; when rubbed with a pestle in a mortar , a strong detonation <a href='uninflect' title='3'><mark>occurs</mark></a> . Black antimony is formed upon rapid cooling of vapor derived from metallic antimony . It <a href='got' title='4'><mark>has</mark></a> the same crystal structure as red phosphorus and black arsenic , it <a href='uninflect' title='5'><mark>oxidizes</mark></a> in air and may ignite spontaneously . At 100 ° C , it gradually <a href='uninflect' title='6'><mark>transforms</mark></a> into the stable form . The yellow allotrope of antimony <a href='drop_aux' title='7'><mark>is</mark></a>the most unstable . It <a href='been_done' title='8'><mark>has</mark></a> only been generated by oxidation of stibine ( SbH3 ) at − 90 ° C. Above this temperature and in ambient light , this metastable allotrope transforms into the more stable black allotrope . 
4 allotropes of antimony r known : a stable metallic form and three metastable forms ( explosive , black and yellow ) . Elemental antimony a brittle , silver @-@ white shiny metalloid . When slowly cooled , molten antimony crystallizes in a trigonal cell , isomorphic with the gray allotrope of arsenic . A rare explosive form of antimony can be formed from da electrolysis of antimony trichloride . When scratched with a sharp implement , an exothermic reaction occur and white fumes are given off as metallic antimony is formed ; when rubbed with a pestle in a mortar , a strong detonation occur . Black antimony is formed upon rapid cooling of vapor derived from metallic antimony . It got the same crystal structure as red phosphorus and black arsenic , it oxidize in air and may ignite spontaneously . At 100 ° C , it gradually transform into the stable form . The yellow allotrope of antimony tdamost unstable . It done only been generated by oxidation of stibine ( SbH3 ) at − 90 ° C. Above dis temperature and in ambient light , this metastable allotrope transforms into the more stable black allotrope .