What type of flowering tree has very dark bark and purple blossoms?

If it's a small tree, it could be the Eastern Redbud. Photos here:

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Could also be a Lilac Tree:

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Purple Flowering Tree

Tree That Blooms Purple Flowers

Yes, also known as a red bud tree. JUDAS-TREE, the Cercis siliquastrum of botanists, belonging to the section Caesalpineae of the natural order Leguminosae. It is a native of the south of France, Spain, Portugal, Italy, Greece and Asia Minor, and forms a handsome low tree v,ith a flat spreading head. In Spring it is covered with a profusion of purplish pink flowers, which appear before the leaves. The flowers have an agreeable acid taste, and are eaten mixed with salad or made into fritters. The tree was frequently figured by the older herbalists. One woodcut by Castor Durante has the figure of Judas Iscariot suspended from one of the branches, illustrating the popular tradition regarding this tree. A second species, C. canadensis, is common in North America from Canada to Alabama and eastern Texas, and differs from the European. species in its smaller size and pointed leaves. The flowers are also used in salads and for making pickles, while the branches are used to dye wool a nan-keen color.

If the blossoms are small and look like little mickey mice and are all along the branches and the tree blooms before the leaves come out and you live in Canada or northern USA than the tree is probably called a red bud tree, which are indigenous to north america. Good luck.

Cherry Trees

lilac bush?