The plural possessive is diamonds'.
The possessive form for the singular noun roof is roof's.The plural form for the noun roof is rooves.The plural possessive form is rooves'.
There are two accepted plural forms of the noun vertex: vertices and vertexes.The plural possessive forms are vertices' and vertexes'.
You have no parentheses, but the sentence does have two plural nouns.The plural possessive forms for those nouns are:paths; paths'circles; circles'
The noun marble is an uncountable (mass) noun as a word for the crystalline metamorphic form of limestone, a word for a substance.The plural form of the noun, reserved for 'types of' or 'kinds of', is marbles.The plural form of the noun marble as a word for a small glass ball used as a toy is also marbles.The plural possessive form (for the substance or the toy) is marbles'.Examples:The marbles' display included an array of lovely colors.The marbles' bag split and the marbles rolled everywhere.
You may be thinking of gemstones and industrial diamonds. Gemstones represent about 20% of all diamonds mined, and the remainder is industrial diamonds.
The possessive form for the plural noun diamonds is diamonds'.Example: I had the diamonds' settings checked by a jeweler.
Singular possessive: secretary's Plural: secretaries Plural possessive: secretaries'
The plural is lads. The plural possessive is lads'.
The plural is relatives. The plural possessive is relatives'.
The plural form is suffixes. The plural possessive is suffixes'.
The plural form is stepsisters. The plural possessive is stepsisters'.
The plural form is Mexicans. The plural possessive is Mexicans'.
The plural form is echoes. The plural possessive is echoes'.
The plural form is inches. The plural possessive is inches'.
Studies' is the plural possessive of study.
The plural possessive is pals'.
Coaster's is singular possessive. The plural is coasters, the plural possessive is coasters'.