When calcium is recommended for osteoporosis, is it a special kind of calcium such as citrate or milate (please forgive incorrect spelling?)

Citrate or carbonate: Either will do, if taken properly and in the correct amount, along with sufficient vitamin d. Check w/your physician.

See below: it is better to get the calcium intake from the diet. Most patients that type of calcium preparation, does not matter. Please find additional information in the following link https://www.nof.org/patients/treatment/calciumvitamin-d/