The black turtle bean is a small, shiny variety of common beans, especially popular in Latin American cuisine, though it can also be found in Cajun and Creole cuisines of south Louisiana.

Black beans (and all common beans) are native to the Americas, but have been introduced around the world.

They are also used in Punjabi cuisine. (source)

So can guinea pigs eat black beans?

We take a look at their nutritional data and find out more.

In particular, their acidic, water, sugar, fat, salt, calcium, and phosphorus content is of most interest as far as guinea pigs are concerned.

Nutritional value per 100 g (3.5 oz)
Energy 552 kJ (132 kcal)
Carbohydrates
23.71
Sugars 0.32
Dietary fiber 8.7
Fat
0.54
Saturated 0.139
Trans 0
Monounsaturated 0.047
Polyunsaturated 0.231
Protein
8.86
Vitamins
Vitamin A 6 IU
Thiamine (B1) (21%) 0.244 mg
Riboflavin (B2) (5%) 0.059 mg
Niacin (B3) (3%) 0.505 mg
Vitamin B6 (5%) 0.069 mg
Folate (B9) (37%) 149 μg
Vitamin B12 (0%) 0 μg
Vitamin C (0%) 0 mg
Vit D (0%) 0 μg
Vitamin D (0%) 0 IU
Vit E (6%) 0.87 mg
Vitamin K (3%) 3.3 μg
Minerals
Calcium (3%) 27 mg
Iron (16%) 2.10 mg
Magnesium (20%) 70 mg
Phosphorus (20%) 140 mg
Potassium (8%) 355 mg
Sodium (16%) 237 mg
Zinc (12%) 1.12 mg
Other constituents
Water 65.74 g

source wikipedia

As you can see, black beans contain a huge amount of water, a lot of salt, phosphorus, a little calcium and acidic content plus a hint of sugar and fat.

This means that they are not a good food for guinea pigs to eat because of their very large water content. They will bloat a guinea pig.

If they nibble one, they should be fine but they are not a food that should be purposely be fed to them.