Chalcedony to as prase. However, the term prase is also used to describe green quartz, and to a certain extent is a color-descriptor, rather than a rigorously defined mineral variety.) Blue-colored chalcedony is sometimes referred to as "blue chrysoprase" if the color is sufficiently rich, though it derives its color from the presence of copper and is largely unrelated to nickel-bearing chrysoprase. Heliotrope is a green variety of chalcedony, containing red inclusions of iron oxide that resemble drops of blood, giving heliotrope its alternative name of bloodstone. In a similar variety, the spots are yellow instead, known as plasma. Moss agate
Spa (mineral water) "Spa red") is a generic term for sparkling water, as the label for sparkling Spa is red. Likewise, "Spa blauw" (pronounced "spah blow" (rhyming with "cow"), and meaning "Spa blue") is a generic term for still (non-carbonated) mineral water, as the label for non-carbonated Spa is blue. In a Dutch restaurant, for example, if a customer wishes sparkling mineral water, he will most commonly ask for "Spa rood". Generally, the waiter would not expect that the customer wants Spa brand specifically, nor would the customer expect Spa specifically. In some cases, customers even refer to tap water as "Spa grey."