पत्थरों के घिसाव प्रतिरोध या कठोरता को निर्धारित करने के लिए किस परीक्षण का उपयोग किया जाता है?

Which of the following artificial stones is produced by moulding a mixture of iron slag and Portland cement?

Enamel paint is generally prepared by adding:

Dorry's testing machine is used for which test on building stones?