What does
isosceles

equilateral

scalene

mean??

All of them are different type of triangle. 1)two sides of equal length 2)  sides of equal length 3) All three sides are in different lengths, and angles are of different measures.

luster is not a good characteristic to use by itself because luster is the property of minerals that indicates how much the surface of a mineral reflects light. the luster of a mineral is affected by the brilliance of the light used to observe the mineral surface.