Where on Github, or elsewhere, can I find the code for core-blocks?

Apparently, at one time, there was a directory of core-blocks for building Gutenberg templates on GitHub, but I’m not finding it anywhere. I talking about core/paragraph, etc.

    array( 'core/paragraph', array(
        'placeholder' => 'Content goes here',
    ) ),
    array( 'core/image', array(
        ...

Thanks!

The core blocks appear to be defined in the Gutenberg repository on Github, in the block-library package here: https://github.com/WordPress/gutenberg/tree/master/packages/block-library/src.