Calcium Carbonate

[little wise owl]

Hello, I know absolutely nothing about chemistry but I have a question about Human Grade Calcium Carbonate vs. a pet reptile product Calcium supplement (which claims to be precipitated Calcium Carbonate)

Now, I've posted this on a few reptile forums with no successful responses other than "FEED THE EXPENSIVE REPTILE ONE BECAUSE IT SAID SO" and I don't particularly want to pay out the butt for a specific calcium supplement when I can spend less for more of a human grade product which is SUPPOSEDLY the same.

Here is the post from my reptile forums:

What's the difference between:

The company NOW's powdered calcium carbonate for humans.

Originally Posted by Description

The powdered form is 100% pure, and free of fillers and preservatives, much lower in cost, easy to digest and can be taken in desired potencies. Powdered vitamins and minerals are truly the best way to take supplements.

-Supports Bone Health
-100% Pure Powder
-High Percentage of Calcium
-Vegetarian Product

Originally Posted by Ingredients

Calcium (from Calcium Carbonate)

Serving Size: 1 Level Teaspoon (3.0 g)
Servings Per Container: 113

Amount Per Serving: 1.2 g (1,200 mg)
% Daily Value: 120%

AND

the recommended:

Zoo Med's Repti-Calcium

Originally Posted by Description

Repti Calcium is an ultra fine Precipitated Calcium Carbonate Supplement. It is a phosphorus-free calcium supplement for reptiles and amphibians. It has a unique shape/high surface area per gram resulting in increased calcium bioavailability.

[addtional information]
"We use only precipitated calcium carbonate which is white in color and is essentially lead free. Pure calcium carbonate is white, not gray. The calcium carbonate particles in Repti Calcium have a unique shape, and an extremely high surface area per gram, resulting in increased calcium bioavailability."

Are there any reasons I COULD NOT use this for a reptile (a large lizard specifically)?