Betty - I agree that is sounds as if it is The Lemoyne Star that you are looking for.
Are you are looking to applique this using Fusible web? or do you want to piece it? There are a few variations some use Diamonds and some use the parallelogram.
These measurements are NOT including any seam allowance - if you are piecing it - you would need to add them. For example, for a 12" block using the diamonds, you would draw a 2.5" by 6" rectangle. In that rectangle the diamond would be 3.5" on all sides.
If you need different measurements - PM me.
Diamond Measurements
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