Tangrams, invented by the Chinese, are used to develop geometric thinking and spatial sense. Seven figures…

Tangrams, invented by the Chinese, are used to develop geometric thinking and spatial sense. Seven figures…

"Orthohombric. Crystals usually short prismatic to tabular. Sometimes quite complex with many prism,…

"The only orthorhombic mineral of importance belonging to the hemimorphic class is calamine. When its…

"Orthohombic, hemimorphic. Crystals usually tabular parallel to the brachypinacoid. They show prism…

"Hexagonal-rhombohedral. Crystals are very varied in habitat, often highly complex. Over 300 different…

"Hexagonal-rhombohedral. Crystals are very varied in habitat, often highly complex. Over 300 different…

"Hexagonal-rhombohedral. Crystals are very varied in habitat, often highly complex. Over 300 different…

Tangrams, invented by the Chinese, are used to develop geometric thinking and spatial sense. Seven figures…

"Tetragonal. Common forms are prisms and pyramids of first and second orders." — Ford, 1912

"Orthorhombic. Crystals resemble closely those of barite. Commonly tabular parallel to the base or prismatic…

An illustration showing how to construct the center and radius of a circle that will tangent a given…

An illustration showing how to construct the center and radius of a circle that will tangent a given…

An illustration showing how to construct the center and radius of a circle that will tangent a given…

An illustration showing how to construct a center and radius of a circle that will tangent the three…

"A crystal has a center of symmetry if an imaginary line is passed from some point on its surface through…

"Habit varied and crystal show many forms. Crystals often tabular parallel to brachypinacoid." —…

"Hexagonal-rhombohedral. Common form is the simple rhombohedron, r, having nearly cubic angles. May…

"Orthorhombic. Usually in small tabular crystals with hexagonal outline. Striated parallel to the brachy-axis."…

"Orthorhombic. Usually in small tabular crystals with hexagonal outline. Striated parallel to the brachy-axis.…

An illustration showing how to construct a circle arc without recourse to its center, but its chord…

Illustration of a circle used to prove "All angles inscribed in the same segment are equal."

Illustration of a circle with an inscribed angle that can be used to prove that "An inscribed angle…